Show hidden files by one click

I would like to toggle whether hidden files and dirs are shown or not by one click. (Generally I don't want to see hidden files, but sometimes I need to delete/move/copy some files with "hidden" attribute.)
I know I can make my own buttons, but I don't know exactly how. I.e. what should I type in "function" field when adding new button.

<?xml version="1.0"?> Hidden/System 84 Set HIDEFILTERATTR HS