Validate value of column in every Datagridview row

Hello,

I have a sql View that returns two columns - 'Item', 'Balance'

Then I have a datagridview with a comboboxcolumn 'Item' that matches the one in the view but is pulled from a different source.

I want to use the View to validate the datagridview column so that before a user saves that I can query every row and in the datagridview and check the 'balances' in every 'Item' is not greater than zero.

I am using a function but when i debig it-i find  its only checking the first row and not going to the next while I want it to check every row 'Item'  in the datagridview

see function code below:

Try
              For Each row As DataGridViewRow In SalesDtlDataGridView.Rows

                Dim cnn As New SqlConnection(My.Settings.TeaTrackingConnectionString)
                If cnn.State = ConnectionState.Closed Then cnn.Open()
                Dim cmd As New SqlCommand("select GardenDtlID,InvoiceNo,BalanceQty from dbo.vwInvoiceBalance where GardenDtlID=" + "'" + row.cells(2)Value.ToString + "'", cnn)
                Dim Inv As String
                Dim Bal As Int32
                Dim dr As SqlDataReader
                dr = cmd.ExecuteReader
                While dr.Read
                    Inv = dr("Item")
                    Bal = dr("Balance")
                End While
                If Bal <= 0 Then
                    Return False
                    Exit Function
                Else
                    Return True
                End If
            Next i
        Catch ex As Exception
            Return Nothing
            MessageBox.Show(ex.Message, "Tea Tracking | ValidateInvQty", MessageBoxButtons.OK, MessageBoxIcon.Error)
        End Try

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