Too Simple to Imagine for this form, but I need help.

[Frans C]

Why don't you pass object variables?
Instead of passing strings, you can pass a Form and a Control object. Even stronger: if you pass a reference to the control, you don't need to pass the form.
eg
Public Function fcnTest(MyControl As Control) As String

fcnTest = MyControl.Tag

End function

You could call the function like this:
strSomething = fcnTest(frmMain.ctlPushButton)
or like this
strSomething = fcnTest(Screen.ActiveControl)