>I need a way to detect whether a given form is currently in use or even better to generate a list of open forms.
>
>The reasons are two-fold. First, I want to restrict the user to one instance of a form and if he tries to open it again, I want the application to detect that fact and activate the existing instance rather than opening a second copy.
>
>Second, I want to be able to do a cleanup procedure when the application is closed. This procedure would close all open forms and notify the user is there is any trouble closing any of the forms.
>
>I cannot find any function or other mechanism to list the open form objects in an application, but I firmly believe that there has to be something.
>
>Thanks for any help.

_screen.forms collection and sys(1271) would help for looping. For first part you don't need to loop and just check :

FormIsOpen=type('SCXName')='O' ;
  and !isnull(SCXName) ;
  and SCXName.Baseclass = 'Form'

Cetin