How do I use a GridView.CommandButton as ModalPopup.OKControlID and populate underlying page with data?

I am using a ModalPopup to display a GridView with a resultset. I want to select a row from the GridView and upon selection have the modalpopup dismiss and populate the underlying page with the data from the gridview row.

I have seen numerous examples of the exact opposite scenario (i.e. using a gridview commandbutton to show a modalpopup), but nothing like what I am trying to do.

Any help is greatly appreciated.