Can I get a url and FTP access to test?
Does it work if you create your own button and window?
When you say it doesn't work, do you mean the window doesn't display or that the delete doesn't work?
I'd get a window to open with the click of a button outside of the webassist code. Then once you are sure the basic concept works you can copy the webassist window content into yours. Then copy and replace the button last.