Sounds like you want to right a bit of javascript so that on the select of a row it calls a populate command to fill the text boxes.
You could of course submit back but I don't think that is really what you are wanting to do and you could use frame and just refresh the frame with the text boxes but it really depends.
If you can post the rendered page (eg. the html etc generated from the asp.Net app) then we should be able to help.
Cheers,
Shaun