I'm developing a form and would like to be able to enable or show a button
after all of the required fields have been filled out.  It does fine the
first time through if I'm looking just for the data being blank but a user
may come back and change one item and I'd like, at that time, to re-enable
the submit button.  It doesn't appear that conditional formatting can detect
a 'change' in the data--specifically if using Forms Services.  

I tried doing this in managed code but failed because I forgot that, under
Form Services, this is a web application and most changes don't force a
postback unless you select 'always' on the Properties->Browser tab for each
control, and then sometimes it still doesn't do it.

Am I missing something here?  Is there a better way to do what I'm talking
about.  Thanks in advance for any help or direction.