VS 2010 update datagridview combobox from a textbox

Hi

i am stuck with a problem i hope the solution may be quit an easy one but could not get it. After searching though varios forums and applying my head to the exhuation i seek my answer here.

Ok now, my problem is that I have a textbox as tb116 ,

a datagridview as tv1 has 5 columns (with column(1)) as datagridviewcomboboxcolumn

bound to datatable as dt ,having valuemember and displaymember defined

and a list as t1

on my form. Now when tb116 gets focus t1 is shown , when t1 is selected or clicked i get text for tb116 and same needs to be shown in column(1) ..further i also want to set text in column(1) from a string or another textbox.....

Pls help it very urgent