Sweep with variable rectangle dimension?

Hi, I'm new to Solidworks and am having a hard time figuring out how to create a sweep where the dimensions of a rectangle change along the sweep.  I created a rectangle and a sweep path, then drew a 3D guide curve to guide the height of the rectangle along the sweep.

This seems very simple, but I just cant get it to work.

Is there another way to do this?

Image is attached

Please let me know if you can help.

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Thanks,

Alex

SolidworksParts And Features