you can set slave ERC code from whatever you want as the master dial.

 

You leave the master dial alone and add this code to the slave channel below the line interpstyle locked

 

valueOpDeltaAdd
                Figure 1
                BODY:1
                Ybend
            deltaAddDelta 1

ybend is the name of the master dial , BODY is the bodypart where the dial is located

deltaadddelta 1 is the amount to change the slave for very 1 unit change in the master so any fraction can be used like 0.5, 1.6 etc or negative values

Theres a document on ERC code that will work in any Poser version.

http://www.atlantis23.com/erc_download.html