Create worksheet in masterfile and add content below existing content

Context: each employee uses the same worksheet stored on a network drive to fill in their daily activities. I want to capture these activities into one masterfile.
I have found some very neat code to copy the content of a worksheet into a seperate masterfile.
Now I want to:
1. create a new sheet in the masterfile (if it doesn't exist) based on the value of cell B7 in the worksheet (a date)
2. in the new sheet of step 1, find the last row that is filled in, leave a row blank and then copy the content of the worksheet into that new sheet (e.g. in the workbook Tom presses CommandButton9 first and copies his activities to A1:M11 in the new sheet of the masterfile, then Frank presses CommandButton9 and copies his activities to A13:M23 etcetera)
How can I accomplish that?
See here for my workbook

Private Sub CommandButton9_Click()
    Dim IntSht As Worksheet
    Dim IntBk As Workbook
    Dim ExtBk As Workbook
    Dim ExtFile As String
     
    Set IntBk = ActiveWorkbook
    Set IntSht = IntBk.ActiveSheet
    ExtFile = "N:\Uren\Master Workbook.xls"
    'Example of dynamic filename: wbName = "NAV SHEET " & Format(Date, "ddmmyy") & ".xls"
    If Dir(ExtFile) <> "" Then
    Else
        ExtFile = Application.GetOpenFilename(FileFilter:="microsoft excel files (*.xls), *.xls", Title:="Please Select A File")
    End If
    On Error Resume Next
    Set ExtBk = Workbooks(Dir(ExtFile))
    On Error GoTo 0
    If ExtBk Is Nothing Then
        Application.Workbooks.Open ExtFile
        Set ExtBk = Workbooks(Dir(ExtFile))
    End If

'Copy Sheet content to new workbook
'Original line:    IntBk.IntSht.Range("DataDump").Copy ExtBk.Worksheets("Raw Data").Range("A" & Rows.Count).End(xlUp).Offset(1)
    IntSht.Range("A11:M21").Copy ExtBk.Worksheets("Sheet1").Range("A1:M11")
    Application.DisplayAlerts = False
    ExtBk.Save
    ExtBk.Close
    Application.DisplayAlerts = True
    Call CreateEmail
    CommandButton9.Enabled = False
End Sub

This code should be integrated above to create a sheet if it doesn't exist

'Create sheetname
Dim strSheetName As String
Dim wsTest As Worksheet
 
Set wsTest = Nothing
On Error Resume Next
Set wsTest = ActiveWorkbook.Worksheets(strSheetName)
On Error GoTo 0
 
If wsTest Is Nothing Then
Worksheets.Add.Name = strSheetName
MsgBox "Sheet " & strSheetName & " created."
End If
 
'Create worksheet with "Bob" if it doesn't exist.
CreateSheet "Bob"