Will this work on an award reservation?

My wife has a category 1-4 e-certificate. If she books the reservation, is there any way to add me and use my marriott number after the reservation is booked?

Not a huge deal, but I'm working on the US grand slam, and if I can buy an incidental during the stay and get it posted to my account instead of hers for a "hit," it would be valuable.

I guess the other way to do this is to enter my frequent flier number in her account for her earning preference, but I thought I read here that that may not transfer correctly.