on the form they give u a list of their different products to check off, that way they can tell u exactly what u need. there's a box that says "other" though. if u check that one off and put down "Roundup ready corn" they might be able to help u out. if they can't do that then they'll probably contact u. i'd give it a shot tho.
this is the form:
http://www.mossyoakbiologic.com/pdf/soilsample.pdf