Is ViewProgressPage a NetWebPage?
A page cannot be embedded on another page, so you can't call a page as an ajax reply.
I recommend you move the "common" part of the page into a NetWebSource - then you can call the NetWebSource from the page itself, and also from this part.
I set a value before the call do
p_web.SetValue('value',12)
SomeNetWebSource(p_web)
cheers
Bruce