Override surcharge with zero value?

An existing condition type with access sequence needs to be overridden with another condition type for which value will be entered manually.

Things work fine as long as both the values are non-zero. (Example: YV02- 26.00% (access sequence) and is overridden with YM02 with 20.00% (entered manually by the user).

Now there is a second scenario, where YV01- 26.00% needs to be overridden with YM01 whose value is 0.00%.

Is there a way we can implement this with standard settings for either condition type or pricing procedure.

Again requirement is ZF02 is to be manual entry.

Any ideas on how to accomplish this? (other than custom routine development)

Thanks,