I need to control 3 identical motors from a HMI. So I make one faceplate of the motor, and 3 buttons for valve 1, 2 and 3. Also I create 3 HMI tags, valve_select for the valve #, Close_cmd_from_fp, Open_cmd_from_fp. My plan is, when the OPEN/CLOSE button is clicked, it will trigger a VB Script, OPEN_CLOSE_GATE_VALVE. In this script, it will read the above 3 tags, send the command to PLC, and write a message to the text field of the HMI. 

But the Text is not updated after open/close on the faceplate. If the VB script is activated by a button, then it can work. It looks like a HMI tag change can not trigger a VB script.

To test whether the HMI tags can receive the click from faceplate, i made two symbolic IO fields under the text. Each time i click the OPEN/CLOSE, they can show NOT PRESSED/PRESSED. This is implemented with a text -list. But the changes of the HMI tags Close_cmd_from_fp and Open_cmd_from_fp, can not activate the VB script. 

If the answer is No, an internal HMI tag can not trigger the VB Script, how can I solve this problem ?  As i have two parameters, valve # and operation, to determine where to send the command.   

My system is TIA Portal V16, Simocode ES V16, WinCC Advanced V16. HMI is Comfort TP900. 

Thanks for your help !!