Add an extention to "Process Multiple Files"

[Scott_White]

I have a file format that I need to convert alot of bmp's and jpeg's to, and I decided to use the Process Multiple files tab...unfortunitely, it doesn't have the format I need. Is there a way I could add it? or do I need to make a script that allows it to have that extra extention

P.S. I'm using Photoshop Elements 4.0 and i have the file extention, but not in the "process multiple files" option.

also...the file extention I am trying to add is vtf, which is a texture extention for the game HL2.