Toggle Button, Focus, Switching Back And Forth

Here's a little design problem, all of my VB script works fine, it's just a design problem:

Toggle Button (onClick) {
if pressed in, unlock protected field, pass focus to protected field
else (if not pressed in), lock protected field
}

Protected Field (lostFocus){
When Focus is lost, protect field then reset toggle button
}
See, there's no way that I know of for Access to tell what field has focus at any given moment. It lies inert until an event fires off then it responds. You can't wake Access up and tell it to go do something. So, Protected Field has to lock itself when it loses focus.

Here's the problem. If a user unlocks the field but then decides not to make a change and clicks the toggle again to lock the field, first Access fires the script to protect the field (locking it), then it resets the toggle button, then it registers the toggle button click which unlocks the field. See the problem? If the user changes their mind about changing the field and then tries to lock the field, it ends up unlocked. I need something that will work whether the user is good about it or whether the user is in a rush and forgets about it.