stop the close of active document...CS3

Hi,
I m new to plugin development. I m using Indesign CS3 on MAC OS.
How do i get the reference(UIDRef) to the active document?
I want to stop the close operation of this document... I have disabled the close menu... But want the close button also to be disabled...
Should i implement IDocFileHandler? or is ther any other way?
Can someone please guide me...
Thank You.