adding ups option with " 0 " price---not working

[treybraid]

i have setup 3 ups options on the website:

1. ups standard ground
2. ups standard overnight
3. ups international

( he is using a fixed amount )

...he now wants to use another one for customers who already have a ups account..so the new one is:
4. use your ups account# ( enter it in the comments ) $0.00

i have gone in a created the shipper and shipping rate's...of course set to " 0 " ... in checkout it is not accepting the " 0.00 " payment...

any idea's... they process all their payments manaually...

thanks
trey