Any way to easily create a constraint that is based on a percentage that work with tables?

The way I'm doing it now is using programming global variables through tables and equations to set the dimensions based on those global variables.

e.g.

"AnglePercentage" = 0.5

"Angle@Something" = "AnglePercentage"*"ReferenceAngle@Something"

Then Angle is easily set using AnglePercentage.

I'm sure this is extremely inefficient.

Any better ways?