recordset problem

hi please guide me how to retrieve sum of field value in recordset

my requirement when i choose item in row level the another one field shows open qty retrieve based on vendor and item

If (pVal.FormUID = "Requisition") And pVal.ItemUID = "REQ_Mat" And (pVal.ColUID = "Col_Item") And pVal.EventType = SAPbouiCOM.BoEventTypes.et_LOST_FOCUS And pVal.Before_Action = False Then

                Try
                    Dim str1, str4 As String
                    Dim oForm As SAPbouiCOM.Form
                    Dim oEdit As SAPbouiCOM.EditText
                    oForm = gonAppApplication.Forms.Item("Requisition")
                    oEdit = oForm.Items.Item("txtsupID").Specific
                    str1 = oEdit.Value
                    Dim iCnt As Integer
                    For iCnt = 1 To gonMatConvMatrix.RowCount - 1
                        gonMatConvMatrix = oForm.Items.Item("REQ_Mat").Specific
                        str4 = gonMatConvMatrix.Columns.Item("Col_Item").Cells.Item(iCnt).Specific.value
                        Dim oRS As SAPbobsCOM.Recordset = gonComCompany.GetBusinessObject(SAPbobsCOM.BoObjectTypes.BoRecordset)
                        If str4 <> "" Then
                            Dim sSql As String = ""
                            sSql = "SELECT T0.[CardCode], T1.[ItemCode],sum(T1.[OpenQty]) FROM OPOR T0  INNER JOIN POR1 T1 ON T0.DocEntry = T1.DocEntry WHERE T0.[CardCode] ='" & str1 & " ' and T1.[Itemcode] ='" & str4 & " 'GROUP BY T1.[ItemCode],T0.[CardCode]"
                            oRS.DoQuery(sSql)
                            For i As Integer = 1 To oRS.RecordCount
                                If oRS.EoF <= 0 Then
                                    gonMatConvMatrix.Columns.Item("Col_PQty").Cells.Item(i).Specific.Value = oRS.Fields.Item("CardCode").Value
                                    oForm.Freeze(False)
                                End If
                            Next
                        End If
                    Next
                Catch ex As Exception
                    gonAppApplication.SetStatusBarMessage(ex.Message)

                End Try

            End If

Thanks & Regards

B.Lakshmi Narayanan