DataGrid and textBox - Mark and Focus

[Gidi]

Hi,

I have DataGrid table and TextBox in my form. the table contains names and i
use the textBox to enter letters to search specific customer. i want that the
user will be able to navigate the DataGrid with the UP and Down arrows while
the focus is on the TextBox and to mark the selected row.

for example, when the form loads,the focus is on the Textbox and the first
row is marked, the textbox is empty. i enter G and the table contains all the
names that begins with a G, the focus is still on the textbox and the first
name that begins with a G is marked, now, i saw that the name i look for is
at the 3rd row, so i want to navigate with the down arrow to this row, and
each time i press the down arrow i want the row i point at will be marked and
if the user will decide to add to the G also I, the focus will be back to the
textBox which will contain now GI.

how can it be done?

thanks,