Checking for multiple dialog instances

I currently have an application with a dialog box descended from
TDialog. I've used Application^.MakeWindow to create it since I don't
want it running exclusively of the main window. My problem now
however, is checking to see if it's already on screen so I don't get
multiple boxes. Is there a value I should be checking? I've tried it
with HWnd (If Hwnd=0 then Active:=FALSE) but that doesn't work.
I'm using a function called Active from within my dialog object to
return a value right after a selection from the main window's menu.
I'm calling Init for the dialog before I make a call to Active.
I frankly don't know what I should be looking at for multiple dialog
instances here. Any help is appreciated.
 Luminous Software Development