Hi Bill, so because your extrusion object has a kind of 2-sided path nature to it, you can use Sweep with a scaling rail like Marco mentions.

But also a common way to get a modified height extrude is to do a regular extrusion first and then slice the top of the extrusion off with the boolean difference command. Usually you would do the cut with a 2D side profile curve as the cutting object, but in your case here the different heights along each station that you want does not correspond to just one 2D side profile, so instead of cutting with a 2D side profile curve you would have to build a cutting surface. In your case here you could use sweep along height curve (with the ends extended slightly) like this:





That needs to extend far enough to all sides to divide the extrusion into 2 pieces.

Then you do the extrusion to make one blocky solid with a uniform height:



Run boolean difference and pick the variable height surface as the cutting object, that will divide the extrusion into 2 pieces:



Delete the piece you don't want to keep:




So with this method you focus more directly on modeling the variable height capping piece itself and it becomes part of your final model after it slices off the extrusion.

- Michael