Can I create message boxes on a yes/no drop down menu with a mac

Hi, Is it possible to create a macro pop-up message box on a yes/no combo drop down selection menu on ms access 2007? I've created a form titled Admin staff and a label text box entitled "Is this a tentative booking?" - when the user selects yes a pop message will be displayed and when the user selects no, again a message box will be displayed with a different message...if so, how can this be done? I've been using code in ms access 2003 which works...but when I implement the code in 2007 I receive error messages. Thanks for your clever suggestions....


Private Sub Combo1_AfterUpdate()

Dim MsgAnswer As Integer

On Error Goto Error_Handling

If Combo1.Value = "Yes" Then
MsgAnswer = MsgBox("Is this a tentative booking?", vbYesNoCancel)
If MsgAnswer = vbYes Then
'Add code to open the form
ElseIf MsgAnswer = vbNo Then
'Add code for selecting No
Else
'Cancel the operation
End If
Else
'Use the above format to code for other situations
End If

Exit Sub
Error_Handling:
MsgBox Err.Description, vbCritical

End Sub