Asking again, if date is not acceptable why offer users a choice? Just tell them they must correct and keep focus on the DtFrom textbox.
Validation Rule and Validation Text properties should accomplish that as well as the BeforeUpdate event.
Did you try the BeforeUpdate event and suggested code? Even if you want to give them a choice, use BeforeUpdate event.
Code:
Private Sub DtFrom_BeforeUpdate(Cancel As Integer)
If Me.DtFrom < Me.SsnStDt Then
If MsgBox("Enter a date between " & Me.SsnStDt & " and " & Me.SsnEndDt & vbCrLf & vbCrLf & "Want to change Date?", vbYesNo, "Wrong Date") = vbYes Then
Cancel = True
End If
End If
End Sub