Dim blnErrorsExist As Boolean = False
    Dim strMsg As String = ""
    Dim strValue As String = ""
    Dim strSQL As System.Text.StringBuilder
    Dim cm As CurrencyManager = _
        CType(DataGrid.BindingContext(DataGrid.DataSource), CurrencyManager)
    Dim intRowCount As Integer = cm.Count - 1
    Dim intRowIndex As Integer = 0
    Dim intRows As Integer = 0
    Dim intColIndex As Integer
    Dim intColCount As Integer = 1
    '
    ' Loop through the datagrid rows.
    '
    For intRowIndex = 0 To intRowCount
        '
        ' Initialize the filter string. Trim values so "JOE" matches "  JOE  ".
        '
        strSQL = "Trim(Cust_Name)='?0' AND (Trim(Cust_Office)='?1' ?2)"
        '
        ' Loop through the row's columns. The key to the Customer table is
        ' Cust_Name. If the key consisted of more than one column you could
        ' easily expand this technique.
        '
        For intColIndex = 0 To intColCount
            '
            ' Get the datagrid cell's value and trim it.
            '
            strValue = DataGrid(intRowIndex, intColIndex).ToString().Trim()

            Select Case intColIndex
                Case 0
                    '
                    ' Customer name is required.
                    '
                    If strValue = "" Then
                        blnErrorsExist = True
                        strMsg = "Missing Customer Name."
                        Exit For
                    End If
                    '
                    ' Build the filter SQL.
                    '
                    strSQL = strSQL.Replace("?0", strValue)

                Case 1
                    '
                    ' The Customer Office can be blank or Null. The filter string
                    ' must catch this and treat the following 2 rows as duplicates:
                    '   Cust Name   Cust Office
                    '   JOE           blank
                    '   JOE           null
                    '
                    strSQL = strSQL.Replace("?1", strValue)
                    If aValue = "" Then
                        strSQL = strSQL.Replace("?2", " OR Cust_Office IS Null")
                    Else
                        strSQL = strSQL.Replace("?2", "")
                    End If
            End Select
        Next

        If blnErrorsExist Then Exit For
            '
            ' Look for duplicate rows by applying a filter 
            ' and checking the number of rows.
            '
            DS.Tables("Customers").DefaultView.RowFilter = strSQL
            intRows = DS.Tables("Customers").DefaultView.Count
            DS.Tables("Customers").DefaultView.RowFilter = ""

            If intRows > 1 Then
                blnErrorsExist = True
                strMsg = "Duplicate row found. The Customer Name" & vbCrLf & _
                             "and Customer Office must be unique."
                Exit For
            End If
        Next
        '
        ' If an error was found go to the bad row and issue a message.
        '
        If blnErrorsExist Then
            DataGrid.Select(intRowIndex)
            '
            ' See text below.            
            '
            DataGrid.ScrollToRow(intRowIndex)
            DataGrid.CurrentRowIndex = intRowIndex 

            MessageBox.Show(strMsg,"Error Saving Data", _
                MessageBoxButtons.OK, MessageBoxIcon.Error)
            Return
        End If