Limit a form to only one instance of a usercontrol

[MarkT]

I have a usercontrol that sub classes the parent form. This is fine unless you try to place more than one on the form. It is easy enough to check if there are any of these controls on the form already and inform the user that they are about to make a big mistake by placing a second one on the form. But, is there a way to stop a second control from being placed on the form?