[Marjon Le roy]

Thanks for the help Dan!
I dove into some math last couple of hours and just figured it out myself. And it is actually quit easy.

For those who want to know how I solved it, this is the formula:
((slider value – start value)/(end value – start value))*100

So my expression looks like this:

slider = thisComp.layer("Control").effect("Slider Control")("Slider");
p = ((slider - 70)/(100-70))*100;