Line Driven Pattern

Folks,

I have a duct I am trying to define in a fairly controlled manner.

I have done it thusly:

1. It follows a specific centerline curve.
2. It varies from an ellipse at one end to a circle (ellipse with Rmajor = Rminor) at the other.
3. I created a curve.
4. Made some points and datums on the curve.
5. Created elippses on each datum using the point as a ref, varied Rmajor and Rminor manually per a spreadsheet

Then used a Boundary Blend to create the duct surface.

Pretty happy with the result.

But... It is not exactly parametric.

I was thinking of trying to use a Pattern, but cannot seem to find a way to change Rmajor/Rminor along the curve.

I did find that pattern along a curve drives the initial pattern nicely, adjusting the "section angle" to remain normal to the curve.

But cant seem to find  a parameter which tells the sketch which pattern instance it is on, which could then be used to change Rmajor/Rminor

Can this be done in ProE?? Or am I chasing my tail?

Thanks

-ANdy