Controls on Multipage PropertyManager Page
All of the controls for a multipage PropertyManager page must be contained
on a single page. Your add-in must:
Simulate the appearance of multipage controls
by showing and hiding the appropriate controls
at the appropriate times.
Only show and hide controls, and possibly initialize
control values, in the previous page and next page handlers.
Your add-in must not respond to the next page handler by trying to show
a second page because:
The first page will close.
When the next page handler returns control to
the SolidWorks application and your code, the first page is gone and a
memory error occurs.