Focus does not move to next new row in grid view when press

Question

I have designed a wpf page. But I not able to set Proper Tab Navigation on Grid view. Controls (grid view) on the page are not following tab index. Page contain Grid and Save,Cancel button.

There is a gridview. This grid has rows and columns. Each row contains 2 autocompletebox and 6 textboxes. When first i enter the value on the first autocompletebox,then enter tab it move to next box and so on. I enter the value in last text box and press enter button, then a new row will be formed in the grid. Then i press the tab it focus move on the outside button(Save button). I want to move the focus on the next box( first autocomplete box,not on the save button) in the second row in the grid.Pls help...