How to prevent entering duplicate record in DataGridView?

    Private Sub grd_RowValidating(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellCancelEventArgs) Handles grd.RowValidating
        Dim row As DataGridViewRow = grd.Rows(e.RowIndex)
        Dim FNameCell As DataGridViewCell = row.Cells(grd.Columns(ColumnEnum.FirstName).Index)
        Dim LNameCell As DataGridViewCell = row.Cells(grd.Columns(ColumnEnum.LastName).Index)
 
        row.ErrorText = ""
        FNameCell.ErrorText = ""
        LNameCell.ErrorText = ""
 
        'Do not try to validate if the cursor is in the "New Row" row.  This row contains 
        '  no data yet.  If we try to validate, the cursor will get locked in that row until 
        '  the user enters some valid values.  This little bit of code will let the user 
        '  arrow back up off of that row without having to enter any data.
        If grd.Rows(e.RowIndex).IsNewRow() Then
            Return
        End If 'grd.Rows(e.RowIndex).IsNewRow()
 
 
        '**********************************************************************************
        '**********************************************************************************
        '**********************************************************************************
        'After the first key is pressed in the "New Row" row, a row is added to the grid and
        '  editing occurs there.  The cursor will then be one row above the "New Row" row.  
        '  Hence, the above check will return false as soon as the user begins entering data 
        '  for a new record.
        '
        'The check for duplicate records must be done here as it is not possible to cancel 
        '  in the other events.  However, the following code will also flag an existing 
        '  record as a duplicate just by attempting to arrow through the rows.  This locks 
        '  the cursor in the row indefinitely.
        '
        'What I need is a way to distinguish existing rows from a row that the user is
        '  adding.
        '**********************************************************************************
        '**********************************************************************************
        '**********************************************************************************
 
        'See if this record already exists.  If so, don't let the user leave the row without 
        '  either changing it or hitting ESC.
        'If frmMain.m_bll.opTechs_isExists(FNameCell.Value, LNameCell.Value) Then
        '    row.ErrorText = "Record already exists"
        '    e.Cancel = True
        'End If
 
        FNameCell = Nothing
        LNameCell = Nothing
        row = Nothing
    End Sub
                                              

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Dim idCell As DataGridViewCell = row.Cells(grd.Columns(ColumnEnum.TechID).Index)
If idCell.Value Is Nothing Then
    'This is a new row that is just being added by the user.
 
    'See if this record already exists.  If so, don't let the user leave the row 
    '  without either changing it or deleting it.
    If frmMain.m_bll.opTechs_isExists(FNameCell.Value, LNameCell.Value) Then
        row.ErrorText = "Record already exists"
        'Setting Cancel to True here will stop the RowValidated event from firing,
        '  so the record will not be inserted into the database.
        e.Cancel = True
        Return
    End If
 
End If
                                              

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