i have fixed like so :
<pre> Public Function Get_Units_By_ItemID(DGV As DataGridView, ByVal ItemID As Integer) As DataTable
Dim dt As New DataTable
p.Get_Units_By_ItemID(dt, ItemID)
If dt.Rows.Count > 0 Then
Dim dgvcc As DataGridViewComboBoxCell
dgvcc = DGV.Rows(DGV.Rows.Count - 1).Cells(2)
dgvcc.Items.Add(dt.Rows(0).Item("UnitName"))
dgvcc.Items.Add(dt.Rows(0).Item("UnitName1"))
dgvcc.Items.Add(dt.Rows(0).Item("UnitName2"))
DGV.ClearSelection()
DGV.Rows(DGV.Rows.Count - 1).Cells(2).Selected = True
End If
Return dt
End Function