Hi,
You can asign the Display and Value Members of the combo and the datagrid will do the match for you as long the field asigned to the comboboxcolum have values of the datasource asigned, like this:
Dim dgvc As DataGridViewComboBoxColumn
dgvc = CType( dgvRO.Columns("cboItemNo"), DataGridViewComboBoxColumn)
dgvc.DataSource = YOUDATASOURCE
dgvc.DisplayMember = "THE FIELD YOU WANT TO DISPLAY"
dgvc.ValueMember = "THE FIELD THAT MATCH IN BOTH TABLES"
This should be before you load you datagrid.
Hope it helps,