Double clicking in checkout_confirmation issue

V1.3.7+ has a java script which prevents an order being placed twice (or more) if the user clicks on the "Confirm" button twice (or more), however it does not work if the user's browser is IE, and we have received several duplicate orders from IE users who admitted they "might have clicked twice".

I've searched the forums, read dozens of threads and found 2 which were relevant:

http://www.zen-cart.com/forum/showthread.php?t=60932&highlight=double+submit
and
http://www.zen-cart.com/forum/showthread.php?t=52894&highlight=checkout_confirmation

but couldn't figure out how to install the "fix".

There are tons of different scripts available from various sources, and the Zen Cart files which would be modified are (I think) pretty much identified in the first post. But, quite frankly, I don't have a clue how and where to make the changes. I'd like the button to become disabled once it's been clicked, ideally to also fade or gray out, but the "zen_draw_form" and "zen_image_submit" have me totally confused.

Does anyone have a nice simple explanation I could follow to accomplish this - it would be most appreciated!