How to aplly one % discountt or tax to a Custom Field Type?

[jazzybcn]

Hello, I want to know if is it possible to apply one % discount or tax to a Custom field type, I know we can apply with categories but with Custom field I don't know if there exist any possibility.
thanks for your answer.

[jenkinhill]

http://forum.virtuemart.net/index.php?topic=79799