ok, thank you for apply me first.

But i also find the special problem. I have a dategridview and 3 fields (DataGridViewComboBoxColumn, DataGridViewComboBoxColumn , DataGridViewTextBoxColumn)
Include currency master and currency exchange rate 2 table.
for example, record. Currid currid2 exrate
-------------------------------------------------------------
USD HKD 7.8
HKD RMB

1. How to use your code to check if currid again entry USD is ok , but entry USD , HKD pop error duplicate.
2. Why use DataGridViewComboBoxColumn control, i can't use e.FormattedValue in dg.CellValidating to checking,
even i select the HKD , then i set break point to see, it also e.FormattedValue =" " .
How to check empty in dg.CellValidating method.


Thank you ~~~