title: proper coding of an editing loop in access vba
body: <p>I have a form access that is accepting data.
  I have a field I want to ensure the user places an "a" or "q" into.
  Assuming they do place an "a" (or "A") or "q" (or "Q") I want to accept that field and upshift it.
  if they place anything else I want to reject it (possibly changing the value to something like "?") and require the fix.
  They should not be able to leave the field until correct.
  OR
  I need to learn the better/correct way to do this.
  Can you advise or point me so I learn to do it right?</p>