can't retrieve selected rows cell value in grid view

yes, yes i have tried a lot as suggested in net but i cant.. my project work is to valid email id's need to separate valid and invalid ids the validated ids are stored in db .. i want to download valid and invalid id in separate using file id.. if i gave max(fileid) it retrieves recently processed id's along with that a little enhancement is to downlaod previously processed ids too..

Anything you have tried so far?