In terms of effort, it is probably better to do something like this:
First, working in the ACCDB file, make a form that does what you want for some people. Call it some name with a 1 at the end, like SpecialForm1.
Next, copy the form and edit it so it does what you want for other people. Call it some name with a 2 at the end, like SpecialForm2.
IF you have some code that would be common to both, make that code generic and pass in the form name (or the form itself ByRef) so the code knows which form it is using.
Now at the point where you would open one form or the other, first decide which of the two forms you will be opening. No form control manipulation, no form diddling, nothing that would make an ACCDE file barf. And the less run-time manipulation you do, the safer and saner your application will run.