Running VBA in excel is too slow, how to make it faster?

Hi I'm not an expert in VBA and is just trying to 'crawl' my way in finishing a project. I have a code for my command button (Button_Submit) and the code is below. The results are too slow before it come up. Can I make it faster? Please help.

Private Sub Button_Submit_Click()
Dim iRow As Long
Dim ws As Worksheet

Set ws = Worksheets("INFLOWS_WC")

'find first empty row in database
iRow = ws.Cells.Find(What:="*", SearchOrder:=xlRows, SearchDirection:=xlPrevious, LookIn:=xlValues).Row + 1

'check for a Date
If Trim(Me.textboxDate.Value) = "" Then
    Me.textboxDate.SetFocus
    MsgBox "Please complete the form!", vbOKOnly + vbCritical + vbDefaultButton1, "Alert!"
Exit Sub
End If

'check for Assistant name
If Trim(Me.textboxAssistant.Value) = "" Then
    Me.textboxAssistant.SetFocus
    MsgBox "Assistant field should never be blank!", vbOKOnly + vbCritical + vbDefaultButton1, "Alert!"
Exit Sub
End If

'check for Term of payment value
If Me.comboTerm.Value = "" Then
    Me.comboTerm.SetFocus
    MsgBox "Term of payment should never be blank!", vbOKOnly + vbCritical + vbDefaultButton1, "Alert!"
Exit Sub
End If

'check for Amount
If Trim(Me.textboxAmount.Value) = "" Then
    Me.textboxAmount.SetFocus
    MsgBox "Please indicate amount!", vbOKOnly + vbCritical + vbDefaultButton1, "Alert!"
Exit Sub
End If

'Check if Card is payment type
Select Case Me.comboTerm.Value
    Case "Card"
        Select Case Me.textboxBatch.Value
            Case Is = ""
                Me.textboxBatch.SetFocus
                MsgBox "Batch No. cannot be empty for Card payment type.", vbOKOnly + vbCritical + vbDefaultButton1, "Alert!"
            Case Else
                Select Case Me.comboDoctor.Value
                    Case Is = ""
                                Me.comboDoctor.SetFocus
                                MsgBox "Please select a Doctor.", vbOKOnly + vbCritical + vbDefaultButton1, "Alert!"
                    Case Is = "WhatClinic", "Others"
                        Set ws = Worksheets("INFLOWS_WC")
                        iRow = ws.Cells.Find(What:="*", SearchOrder:=xlRows, SearchDirection:=xlPrevious, LookIn:=xlValues).Row + 1
                        ws.Cells(iRow, 1).Value = Me.textboxDate.Value
                        ws.Cells(iRow, 2).Value = Me.textboxFirstname.Value
                        ws.Cells(iRow, 3).Value = Me.textboxLastname.Value
                        ws.Cells(iRow, 4).Value = Me.textboxTreatment.Value
                        ws.Cells(iRow, 5).Value = Me.comboTerm.Value
                        ws.Cells(iRow, 6).Value = Me.textboxBatch.Value
                        ws.Cells(iRow, 8).Value = Me.textboxAmount.Value
                        ws.Cells(iRow, 9).Value = Me.comboDoctor.Value
                        ws.Cells(iRow, 11).Value = Me.textboxAssistant.Value

                        MsgBox "Entry added to Inflows (WhatClinic) database.", vbOKOnly + vbInformation, "Data Added"

                        Me.textboxDate.Value = ""
                        Me.textboxFirstname.Value = ""
                        Me.textboxLastname.Value = ""
                        Me.textboxTreatment.Value = ""
                        Me.comboTerm.Value = ""
                        Me.textboxBatch.Value = ""
                        Me.textboxAmount.Value = ""
                        Me.comboDoctor.Value = ""
                        Me.textboxAssistant.Value = ""
                        Me.textboxDate.SetFocus
                    Case Else
                        Set ws = Worksheets("INFLOWS_PERSONAL")
                        iRow = ws.Cells.Find(What:="*", SearchOrder:=xlRows, SearchDirection:=xlPrevious, LookIn:=xlValues).Row + 1
                        ws.Cells(iRow, 1).Value = Me.textboxDate.Value
                        ws.Cells(iRow, 2).Value = Me.textboxFirstname.Value
                        ws.Cells(iRow, 3).Value = Me.textboxLastname.Value
                        ws.Cells(iRow, 4).Value = Me.textboxTreatment.Value
                        ws.Cells(iRow, 5).Value = Me.comboTerm.Value
                        ws.Cells(iRow, 6).Value = Me.textboxBatch.Value
                        ws.Cells(iRow, 8).Value = Me.textboxAmount.Value
                        ws.Cells(iRow, 9).Value = Me.comboDoctor.Value
                        ws.Cells(iRow, 11).Value = Me.textboxAssistant.Value

                        MsgBox "Entry added to Inflows (Personal) database.", vbOKOnly + vbInformation, "Data Added"

                        Me.textboxDate.Value = ""
                        Me.textboxFirstname.Value = ""
                        Me.textboxLastname.Value = ""
                        Me.textboxTreatment.Value = ""
                        Me.comboTerm.Value = ""
                        Me.textboxBatch.Value = ""
                        Me.textboxAmount.Value = ""
                        Me.comboDoctor.Value = ""
                        Me.textboxAssistant.Value = ""
                        Me.textboxDate.SetFocus
                End Select
            End Select
    Case "Check"
        Select Case Me.textboxBatch.Value
            Case Is = ""
                Me.textboxBatch.SetFocus
                MsgBox "Batch No. cannot be empty for Check payment type.", vbOKOnly + vbCritical + vbDefaultButton1, "Alert!"
            Case Else
                Set ws = Worksheets("INFLOWS_WC")
                        iRow = ws.Cells.Find(What:="*", SearchOrder:=xlRows, SearchDirection:=xlPrevious, LookIn:=xlValues).Row + 1
                        ws.Cells(iRow, 1).Value = Me.textboxDate.Value
                        ws.Cells(iRow, 2).Value = Me.textboxFirstname.Value
                ws.Cells(iRow, 3).Value = Me.textboxLastname.Value
                ws.Cells(iRow, 4).Value = Me.textboxTreatment.Value
                ws.Cells(iRow, 5).Value = Me.comboTerm.Value
                ws.Cells(iRow, 6).Value = Me.textboxBatch.Value
                ws.Cells(iRow, 8).Value = Me.textboxAmount.Value
                    ws.Cells(iRow, 9).Value = Me.comboDoctor.Value
                    ws.Cells(iRow, 11).Value = Me.textboxAssistant.Value

                    MsgBox "Entry added to Inflows (WhatClinic) database.", vbOKOnly + vbInformation, "Data Added"

                Me.textboxDate.Value = ""
                Me.textboxFirstname.Value = ""
                Me.textboxLastname.Value = ""
                Me.textboxTreatment.Value = ""
                Me.comboTerm.Value = ""
                Me.textboxBatch.Value = ""
                Me.textboxAmount.Value = ""
                Me.comboDoctor.Value = ""
                Me.textboxAssistant.Value = ""
                Me.textboxDate.SetFocus
        End Select
    Case Else
        Set ws = Worksheets("INFLOWS_WC")
                iRow = ws.Cells.Find(What:="*", SearchOrder:=xlRows, SearchDirection:=xlPrevious, LookIn:=xlValues).Row + 1
                ws.Cells(iRow, 1).Value = Me.textboxDate.Value
                ws.Cells(iRow, 2).Value = Me.textboxFirstname.Value
                ws.Cells(iRow, 3).Value = Me.textboxLastname.Value
                ws.Cells(iRow, 4).Value = Me.textboxTreatment.Value
                ws.Cells(iRow, 5).Value = Me.comboTerm.Value
                ws.Cells(iRow, 6).Value = Me.textboxBatch.Value
                ws.Cells(iRow, 8).Value = Me.textboxAmount.Value
                ws.Cells(iRow, 9).Value = Me.comboDoctor.Value
                ws.Cells(iRow, 11).Value = Me.textboxAssistant.Value

                MsgBox "Entry added to Inflows (WhatClinic) database.", vbOKOnly + vbInformation, "Data Added"

                Me.textboxDate.Value = ""
                Me.textboxFirstname.Value = ""
                Me.textboxLastname.Value = ""
                Me.textboxTreatment.Value = ""
                Me.comboTerm.Value = ""
                Me.textboxBatch.Value = ""
                Me.textboxAmount.Value = ""
                Me.comboDoctor.Value = ""
                Me.textboxAssistant.Value = ""
                Me.textboxDate.SetFocus
End Select
End Sub