Assing Shopper Group ON Registration

[tarku]

HI

Is it possible that to assign shopper group on Virtumart Registration For example if the shopper enters his Tax id on registration form then he will be Wholesaler else he will be default shopper
My virtuemart version is 2.0.18(a) and joomla is 2.5.9 and PHP is 5.3.18
Please help