I have a popup window for reminders that opens a new MDI window. If someone has a modal window open then the program will halt with an error that the application is not active. I found the following code to prevent this issue. ( from the newsgroups )
Global Map:-
module('win32')
apiGetFocus,long,pascal,name('GetFocus')
apiIsWindowEnabled(long hwnd),long,pascal,name('IsWindowEnabled')
end
in code
if apiIsWindowEnabled(frame{prop:handle}) <> 0 and apiGetFocus() <> frame{prop:handle}
end