Are you brining in the Inputs and outputs on the Modbus? If so, then use the:
y=GetInput(x) 'x is the "Index number" of the modbus register your brining in
FeedOver=(y/*****) times 100 '****** this is your diverder it will be a number = to how many bits are in your register type (8, 12, or 16 bit), and give you a number 1-100
SetUserDRO(1200, FeedOver) ' sets a user DRO to what your over ride is
SetModOutput(x, *****) 'This sets a 16 bit, word going out to "Index x", if you need to use less than 16 bits(native Modbus output is hex), use bit masking.
Scott