> - access a client-side control reference from the server

You don't.

> - pass client side values to the server within the same html document?

There are several ways that you can do this. You can use DHTML and
scripting to drive some ActiveX or Java Components that can communicate
with the server.

For data access you might look at RDS, but it's not what I would call
ready for production today.

If you want to use VFP on the client side (and even if you don't) you
might want to take a look at the Distributed HTTP Applications article
on my Web site at:

http://www.west-wind.com/articles.asp

This article describes how you can do messaging from the client to the
server over HTTP with some examples on how to drive both data and code.
The doc talks about VFP->VFP on the server, but the same logic applies
regardless of what tools you use.