[ms_access] Condition navigating between Controls

[kenaf42]

I have a form in access 2007, with several controls. I used the On Exit Event 
Procedure for navigating among controls.
Example:
If Method of Payment = "Check" Then
Check No.Set Focus
End If
If Method of Payment = "Credit Card" Then
Credit Card Name.Set Focus
End If
End Sub
And so on for all controls. Form functioned well for months, however today went 
wild. Navigation order does not execute Event Procedure it follows exactly the 
order of TAB ORDER DIALOG BOX.
Please advice