post return to previous scrolling position

When dealing with extra-long forms on pages that scroll, it is
sometimes
(inconvenient but) necessary (if not using asynchronous messaging)
to make a post (in order to update a remote schema) and then repaint
the current page.

However, if the post was generated by an onchange or mouseover event,
inside a long form, the screen usually repaints at the top of the
current
page--not recreating the the scrolled-to state that existed when
the post event happened.

So, posts like that end up jiggling and repositioning the screen,
which is annoying. Is Ajax the only solution?
Or is there a way to return from a post to a previous scroll position,
inside an extra-long form?

Maybe this is a complex html, javascript and server-side scripting
question, all rolled into one. But there is no such group.
There must be a way to do this.