Free shipping option, disable one other shipping option

Hello,
I'm using the free shipping option module, so when the order qualifies, this option as well as all my other shipping options appear on the check-out page. What I want to do, when free shipping applies, is take out one of these other options, while leaving the others available...
I guess I have to add a code to the shiping module I want to disable, but I have no idea what it should be...
Could someone help me ?
Thank you !

I'm wanting to do exactly the same, so help would be doubly appreciated!
I'm using Zencart 1.5 and want Standard Delivery to disappear when Free is activated by spending enough, but still show the option of Express delivery,
Many thanks in advance.

OK, found a way to do it (not sure if it's the best though):

1. Turn off all Free shipping modules.
2. Still in 'Shipping Modules', use 'Table Rate' to set up a delivery price of £5 if order total is up to £65, £0 if order total is £65 – £10,000 [65:5.00,10000:0.00]
3. Keep original cloned Flat rate for Express delivery

This works for me, now depending on order toal you see either £5 Standard / £7.95 Express; or £0.00 Standard / £7.95 Express.

Saves touching any code - a big plus for me!!

Though still have problem that when you go to the checkout (step 1 of 3) neither radio button is selected - it does force you to make a choice but I still thinks it's confusing.