Maintain Proportion Between Function Points

I have a little patch that lets me randomize the points of a function object. The problem I'm having is in keeping the points in proportion when I want to change the overall length (x domain) of the function table. The sub patch "function_shift" contains the scale objects that keep each point as a third of an overall length of 1 second. But how to have these scale objects scale(!) to a variable length?

Thanks

Dave