MS Access - Cancel the Before Update event

I have the following code in the BeforeUpdate event of a combo box on my main form…

Private Sub ResBox_BeforeUpdate(Cancel As Integer)

Dim Resp
Dim MyUpdate As String
Dim MyDate As Date

MyDate = Format(Date, "Short Date") & " " & Format(Time(), "Long Time")

Resp = MsgBox("Do you want to update the Resolution?", vbYesNo)
If Resp = vbNo Then
    Exit Sub

ElseIf Resp = vbYes Then
    Do other stuff
End If

End Sub

The problem is the bold line. No matter what I do I cannot find a way to cancel the event and make the combo box NOT update. I’ve also tried…

Cancel = True

to no effect.

As an addtional hint, after clicking No in the message box, I cannot move to the next record or to another control without the messagebox re-appearing.

So how do I undo the update to the combo box?

Just as an FYI for anyone following ths or with a similar problem…

I just needed to add “Me.Undo” right before the line “Cancel = True”