Question on OPC (OLE for Process Control) When a button is pressed the following will be executed. Updating the value 4 times but the callback function in the client is only called once. Why? ////////////// void __fastcall TForm1::ButtonStartStopClick(TObject *Sender) { ....... UpdateTag (m_StatusTag->Handle, m_StatusTag->Value, OPC_QUALITY_GOOD); m_StatusTag->Value.vt = VT_I2; m_StatusTag->Value.intVal = 0; UpdateTag (m_StatusTag->Handle, m_StatusTag->Value, OPC_QUALITY_GOOD); m_StatusTag->Value.vt = VT_I2; m_StatusTag->Value.intVal = 1; UpdateTag (m_StatusTag->Handle, m_StatusTag->Value, OPC_QUALITY_GOOD); m_StatusTag->Value.vt = VT_I2; m_StatusTag->Value.intVal = 2; UpdateTag (m_StatusTag->Handle, m_StatusTag->Value, OPC_QUALITY_GOOD); m_StatusTag->Value.vt = VT_I2; m_StatusTag->Value.intVal = 3; UpdateTag (m_StatusTag->Handle, m_StatusTag->Value, OPC_QUALITY_GOOD); } /////////////// The callback function is called only once even though the value is changed 4 times in the server.Why is this so???Am I missing something?I,m new to this opc thing //////////////////////// void CALLBACK OPCUpdateCallback (HANDLE hGroup, HANDLE hItem, VARIANT
*pVar, FILETIME timestamp, DWORD quality) { Form1->OPCDataUpdate (hGroup, hItem, pVar, timestamp, quality); } ///////////////////// Any help would be much appreciated