I have a form, which contains a tab page, from which a user can select a patient record and then open one or more data maintenance forms related to the selected patient. They are allowed to have multiple forms open but I don't want them to have one form open for one patient and another form open for a different patient. If the user comes back to the patient selection form while one of the maintenance forms is still open, I want to disable the patient selection grid. I have tried FormName.Activated(), FormName.Enter() and TabPageName.Enter() but none of them fires when I reactivate the form. I have managed to handle this another way but I'm sure I will need this behavior for something else one of these days. Where do I capture the reactivation of an open form? Thanks.