Aligning the pivot point on angled control surface

Is there an easy way to align the pivot point for a control surface that is angled but you don't know what the angle is coz you've only just cut the surface out... er, YKWIM.
Can I align to a particular face or edge?
GMAX 1.1 BTW.
Thanks
Kev
Can I align to a particular face or edge?
GMAX 1.1 BTW.
Thanks
Kev