Access 2007 form: event AFTER undo - forms

Question

I have a form in Access 2007, which has an "update" routine, that enables or disables certain textboxes based on values in other fields (textboxes, checkboxes, comboboxes). The regular operation of that routine works well.
Now I found that pressing ESC calls the undo function, that restores the original values in all fields. But this undo does not call the events on those fields, so the form is in a wrong state, where textboxes are disabled/enabled although they shouldn't.
I also found that there is an undo-event, but that is useless for me because it is called before undo. I need an event after undo. What can I do here to update the fields when ESC is pressed?

Answer 1

I like this solution more, because it works not only on the "ESC"-Key:
private Sub form_Undo(cancel as integer)
afterUndo = true
TimerInterval = 1
end Sub
private Sub Form_Timer()
if afterUndo then
'do something after the Undo-Event
end if
TimerInterval = 0
end Sub

Answer 2

Well, like many times before I have an idea for a solution after postion the question.
The solution here is enabling KeyPreview on the form and using the KeyUp event. The undo is called on KeyDown, so when KeyUp is raised, the form already has the restored values again and the update routine works.

Answer 3

Another solution to this problem is to use each control's OldValue property. Through experimentation, I've found that the three different value properties of controls come into play in different situations:
Control.Value or simply Control
The control's current value most of the time
When the control has focus, it is the value the control had before gaining focus
During a Form.Undo event, it is the value the control prior to the Undo
Relevant during the Control.AfterUpdate and Control.Undo events
Control.Text
The control's value while it has focus
Relevant during events that occur as the user types, such as Control.Change, Control.KeyUp, Control.KeyDown
Control.OldValue
The value the control had when the current record was first opened
Also the value that a form-level Undo will reset the control to
Relevant during the Form.Undo event
The timer-based answer to this question is my go-to solution, but if you're already handling events as the user types (e.g., for live validation), then code like this can be sensible:
Private Sub LastName_Change()
ValidateLastName SourceProperty:="Text"
End Sub
Private Sub LastName_Undo(Cancel As Integer)
ValidateLastName SourceProperty:="Value"
End Sub
Private Sub Form_Undo(Cancel As Integer)
ValidateLastName SourceProperty:="OldValue"
End Sub
Private Sub ValidateLastName(SourceProperty As Variant)
Dim LastName As String
Select Case SourceProperty
Case "LastName"
LastName = Nz(Me.LastName.Text, "")
Case "Value"
LastName = Nz(Me.LastName.Value, "")
Case "OldValue"
LastName = Nz(Me.LastName.OldValue, "")
Case Else
Debug.Print "Invalid case in ValidateLastName"
Exit Sub
End Select
' <Do something to validate LastName>
End Sub
Note that this method does not get you access to the post-Form-Undo value of Control.Column(x) of combo/list boxes. You can get it by using DLOOKUP on Control.OldValue, but you're probably better off just using the timer-based solution instead.