tab completion vs. ESC-ESC

[Matt Hillebrand <hill9361 uidaho edu>]

The file selection widget offers tab completion, which is very nice, but I
find it frustrating that I can't tab over the the CANCEL button
immediately after the window is created. 

Is there a way to make file completion activate on ESC being pressed twice
so that I can use the TAB key to cycle through the buttons (or widgets) in
the file selection window?

Thanks,

Matthew P. Hillebrand