the GetMasterOutput was/is for the "Older" modbus module, (not the serial plugin or TCP).
to get to that data:
MainPlanner->ModOutputs
//x = your index on the outputs 0-127
MainPlanner->ModInputs[y];
//y = your index on the inputs 0-127
to get to the newer stuff for the plugin serial and tcp the data structors are different, AND, the newer
Modbus stuff, is not linked at current time to the VB scripter functions.
scott