I am trying to use the if function on my userform to only allow certain values to be returned from the input of other values on the userform. I also want a message box to appear if certain fields are left blank based upon which data has been entered. Here is my code, but even when I have data input into the "Valve Position" combo box it still tells me "Data needed" Why?

Here is just an excerpt of my code:
If Me.ComboBox_Isolationtype.Value = "" Then
        MsgBox "Please enter data", vbExclamation, "Isolation Data Needed"
        Me.ComboBox_Isolationtype.SetFocus
        Exit Sub
    End If
    
    If Me.TextBox_Material.Value = "" Then
        MsgBox "Please enter data", vbExclamation, "Isolation Data Needed"
        Me.TextBox_Material.SetFocus
        Exit Sub
    End If
    If Me.TextBox_IsolationLocation.Value = "" Then
        MsgBox "Please enter data", vbExclamation, "Isolation Data Needed"
        Me.TextBox_IsolationLocation.SetFocus
        Exit Sub
    End If
    If Me.ComboBox_Isolationtype.Value = "Valve" Or Me.ComboBox_Isolationtype.Value = "Electrical" Or Me.ComboBox_Isolationtype.Value = "Air Mover" Or Me.ComboBox_Isolationtype.Value = "ARP Valve" Or Me.ComboBox_Isolationtype.Value = "Globe Valve" And Me.ComboBox_Valveposition.Value = "" Then
        MsgBox "Please enter data", vbExclamation, "Isolation Data Needed"
        Me.ComboBox_Valveposition.SetFocus
        ElseIf Me.ComboBox_Isolationtype.Value = "Valve" Or Me.ComboBox_Isolationtype.Value = "Electrical" Or Me.ComboBox_Isolationtype.Value = "Air Mover" Or Me.ComboBox_Isolationtype.Value = "ARP Valve" Or Me.ComboBox_Isolationtype.Value = "Globe Valve" Then
        Me.ComboBox_Valveposition.Value = "Closed" Or Me.ComboBox_Valveposition.Value = "Opened"
        Exit Sub
    End If
    If Me.ComboBox_Type.Value = "" Then
        MsgBox "Please enter data", vbExclamation, "Isolation Data Needed"
        Me.ComboBox_Type.SetFocus
        Exit Sub
    End If
Any advice?

Thanks in advance.