How about this? It seems to work for me.

Private Sub txtStartDate_Exit(ByVal Cancel As MSForms.ReturnBoolean)

On Error GoTo ErrThisSub

If Len(Me.txtStartDate) 0 Then
Me.txtStartDate = DateValue(FormatDateTime(Me.txtStartDate, vbShortDate))
End If

Exit Sub

ErrThisSub:
MsgBox "Unexpected error formatting Start Date entry." & vbCrLf & _
"Error: " & Err.Number & "-" & Err.Description
Me.txtStartDate.Value = ""
Cancel = True
Resume Next
End Sub

Where txtStartDate is the name of my textbox control on my form. The
FormatDateTime function takes just about any string that could be formatted
to a date and returns a valid date type. Even the strings 39931 becomes
4/27/2009.

John

"Ueli Werner" wrote:

Hi newsgroup

In my excel form I have a textbox where a date value can be entered. When I
enter a wrong value excel crashes.

Now I like to validate this entry with some kind of entry mask. I like to
verify that the entered value cannot be someting other than a date?

Is there a possibility to do this in excel?

Thanks alot

Ueli Werner