Thanks to all for the quick response, much faster than I could try them. 

I just tried a slight variation on lesbentley’s example and it appears to do what I want, although I’ll need to tune it a bit.  It’s simple and nice, essentially providing a mathematical offset to the control signal, a function sorely missing from the Poser toolbox.

As to the other suggestions, I knew of the atlantis site and have looked through the examples but didn’t immediately see what I was looking for.  I know what ockham means by headaches, but I’ll look closely at the blinds control.  I’m sure I’ll someday need a more complex operation than my relatively simple one.

Thanks again.

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