dropdown in gridview

Question

Hi all, I am a newbie in dotnet. I need to know how to bring about a dropdown list in the first column of gridview. I also desire to know on click of the Submit button, each rows selected value of the dropdown. If possible, when the user selects a value in the first row dropdown, that value must be removed from the second rows dropdown. Thanx for any help in advance. I am using ASP.Net (C#). I would be oblidged if explained with code. Regards, tvks