Comments by Dougie the P (Top 4 by date)

You need to use an UPDATE statment not a INSERT statment in your trigger to update the QID,QNo,QID_No columns in the inserted record rather then insert a new row.

if the data represented by DVGPO.Rows is the detail records of a PO and you want the PO header information saved with each detail row, then move the comd.ExecuteNonQuery() line inside the for next loop. If not then a rethinking of the database structure maybe required. there is not enough information supplied in the question to properly evaluate your intentions.

The important comments by Wes should also be taken in to consideration

Thanks Sergey, I Have done so.