There is no easy way to dynamically adjust the number of points you're adding to behavioral score in the way that you've described.
But this seems overly complicated - why would you want to do this in the first place? What are you trying to accomplish by creating this artificially complicated rule to your system?
Doesn't feel like the effort to do this would generate the relatively equivalent amount of business value.
Jessica - I just ended up creating a trigger that runs every time the lead score exceeds 100 points. It resets both the behavioural and the lead scores to 100, and leaves demographic as is. I didn't end up bothering with getting it to sum.
Grant - we just want our scores to sum. What's the point of having a lead score that is the sum of demographic and behavioural (which is a pretty stock-standard lead score logic) if they don't actually sum?
In the end, our demographic only makes up a small portion of our total lead score (which is behavioural based), so I decided not to worry about it, as it doesn't cause any issues with the overall logic.