how to make slider ctrl for expression

[ela1995]

I have 3 different geometry I want to copy onto grid's point, I use Copy Stamp with this function: fit01(rand($PT),0,1). I also write the expression on switch VOP like this: stamp('../copy1', random,0). Now I can control the variety as well as the randomness by adding values into expression above. But later I need to put all the controls into a controller so the third person can control it easily. Is there a way to make those expression has a slider control so that I don't have to go back to the node to change the number. I would like to make it have a slider like writing chf('offset').

how to make slider ctrl for expression.hip