You mean like the way the Access Startup dialog box expands when you click the Advanced... button? Ok.
This is actually changing the window size, not the form size. The form is what displays inside the window, and has controls on it. The window is basically just the frame.
If you make the form longer, the extra space will be empty (no controls), and will still be hidden unless you also enlarge the window. It's as if the window was a viewport through which you're looking at the form. If the form is bigger than the window, you have to enlarge the window to see more of the form.
Changing the window size is easy: just set the form's WindowHeight and WindowWidth properties at run time. You'll have to experiment a little bit to get the size right. Or, you can use the Size To Fit Form command as I mentioned above to make the window bigger (but not smaller). Rick Sprague