Evaluating a curve based on z coordinate of point on curve rather than its length along curve

Hi there, 

New to grasshopper and need some help. 

I have a a list of points that span along a series of arches in increments. With some help I have made these points using evaluate curve and then changing the range. 

However I want to change the domain from the percentage of the total length of the curve, to the distance of the z coordinate of each point. 

So, instead of the domain being 0 - 0.37, I want the domain to be 0 - 5500 mm off the ground. I hope this makes sense.