Sylvester Marshall

I'm new to PLC Communication and would like to request any / all required help to resolve the current crisis. Pls. excuse my technical write-up and do correct me if I'm wrong. We are using IGSS SCADA with the V120 PLC. Communication is on RS432. I'm able to read the MI values in a Analog Object in the SCADA System by giving the PLC address as "Holding Register 3/16" and Address as 101, '40' being the prefix. This value at location MI 101 is constantly changing and there is no problem in reading the same. When I press the enable/disc button (which is a toggle button) the counter (MI 101) starts / stops. Kindly let me how do I get access to this 'enable/disc' key thru the SCADA System so that I'm able to issue the 'COMMAND' thru a Digital Object to Start/Stop the MI 101 Counter. Would appreciate your guidance. Thanks and Regards .