gridview search

Question

hi every body I have grid view where I need to make search in the first cell the other cells in the same row  autocomplete on first cell search I can only edit

quantity number and jumped to the second row to search for anew product and so on My problem happened when I return back to edit quantity in any previous row and try to add new product it repeat data  in row edited or happened when I use arrows

this is my form where is the problem I need to know how to solve this  problem and why it happened  

 http://www.mediafire.com/download/cweih3zc4pth4xi/Market+2.zip