Possible (if unwieldy) solution:
Take screenshots of your average button with printscreen and edit in paintbrush.
Take one of button pressed, button normal, etc. Edit the flashing and nonflashing states.
set a timer to swtcih the flash/no flash images every N intervals. Make it do this by calling aln alias that checks the mouse isn't down, as that'd mess up your effect a little.
Its messy. Its bulky. It can work tho.
