To pin some points on a vellum cloth, to an animated geometry, I tried these steps:
1) I add a “Vellum Attach to Geometry” SOP. 2) I grouped boundary points (“pin” group) on my cloth geometry. 3) In “Target Path” on “Vellum Attach to Geometry” SOP, I set path of my animated geometry.
I think I made that work once, but actually much easier is to use the Pin to Animation in the Cloth Constrain type directly, and set the Match Animation to “On”