Can't get into scope customer profile billing fields other than address component field

ok, here is the thing.

In the billing profile type I added a text field. What i need to do is to apply a tax base on the value the user enters in this field. The problem is I can't find the right condition that bring into scope this text field.

"The order address component comparison" condition doesn't add this new text field into its list.

What i should do? I am struggling with this three whole days but none of my tries works....

Posted: Feb 29, 2012