So, I don't know How better I can explain it in Houdini terms, but I guess the attached file might give you some sense of what I am trying to achieve.
I have tried to expand group using slider but not only it works in unidirectional manner but It didn't give me much control and smooth transition I would like it to have. The slider works in steps, I would like to replace the slider with a ramp which can work in both directions, and I can easily control the transition from any position throughout the curve.
sim_Curves.hip