Of course, screw-ups always happen when you're just about finished. It's Murphy's Law!
I'm not certain about this, but I doubt that making the subform invisible will solve it. Even if it's not visible it's there.
How do you enter the subform? Do you tab from one control to another in the main form and then tab into the subform? Do you click directly in the subform at any point you wish?
When I look at your code you are already in the subform when it fires. And it's saying, "If you're here, you're here, so set the focus to here" so to speak. A bit circular.
The second part says "If you're not here legitimately, then get the heck out and go back there" so to speak. That seems okay, except Access is funny about SetFocus stuff. Perhaps rightly so, to avoid problems.
Is there any way you can set something in the Main form, so that you can't enter the Subform unless at least one of those 4 check boxes have been checked?
I'm still wondering about that code line
If Me.Parent!Check206 = True Or Me.Parent!Check208 Or Me.Parent!Check227 Or Me.Parent!Check210
Would you not have to add = True after each of the other 3 checks, and not only after the first one?
Just brainstorming here.
Tom