将焦点移动到DataGrid（WPF）中新行的第一列

I am binding a DataTable to a DataGrid(WPF toolkit) for add, edit and delete. I am able to use tab keys to navigate through the cells from top to bottom. But as soon as I press tab on last rows' last column, it is not taking the cursor to the first cell of new row. How can I achieve this?(WPF tool