Controlling Complex Web Form

I have a rather large progressive web form. That is to say that as the form progresses in status, more of the form becomes 'available'. I want to be able to control the form fields depending on the status as follows:

Status: <SELECT> list with <OPTION>'s such as Stage1, Stage2, Stage3 and Stage4 (always available)
If Stage1 is selected, then only the first part of the form is available - maybe form items 10-20. The rest of the form should be visible, but readonly)
x days later, the status is then changed (by user) to Stage2 at which point both the first (10-20 items) and second (21-32 items) are available. Again, the rest of the form visible, but readonly.
This then continues right through all the status levels.

I think that I could figure this out, but just wanted some input into how YOU would go about this in the easiest, most efficient way. Also, should I control the form with client-side Javascript or server-side asp ???

Any thoughts, ideas, recommodations would be much appreciated. Sample script or links would be even better.

That is one possibility, but if the user changes the status, the page will need to be reloaded.
Before that happens, I will need to write any changes to the database (does the user want to commit changes???). 

Therefore, maybe Javascript would be better???

What I am after from this thread is a discussion on what you guys would do. Also, the pro's and con's of the various available options.

My vote is for server side. Simply break the steps into separate pages and show what is applicable on that page. Store the current status in a database or file somewhere.

A rule of thumb I try to remember is to not cause the user to scroll down more than 1 page (for average resolution) for any pages on the site. There are exceptions of course, but this might help in your case.

Cheers,
Andrew