This is for an SDrive site, so no Website Access Manager or outside PHP scripts will work.
Can I do this with Formbuilder?
1. Enter a password
(Regex to confirm, and if OK...)
2. Click button to go to a webpage (rather than submit the form)
This is so customers could enter a discount code and then click to go to a special discounts page not available to the public. It doesn't have to be real secure, but the site owner would like to run promotions from time to time and just change the discount code word as needed.

If I'm following you correctly you would send the proper code out to certain users then they would go to the form and submit it which in turn will redirect them to the special. Yes that would work because only the code provided by you would match the reg expression.

And if that doesn't work ... [removed rival software info due to FB having the possibility to do what the OP asked for]

All tools are FREE to a certain level. All use simple html code, no php. I've used them for years.

Gunsmoke, I was looking at the [removed rival software info due to FB having the possibility to do what the OP asked for] site and saw this:
*$24.95/year or FREE with Professional [other software] Membership ($5/month)
and then this:
It is completely free to become a [other software] member. Once you have registered an account will be setup for you and you can start using our tools.
So I can't figure out what this will or won't cost

On the other hand... I have FB, I just don't know how to do anything beyond simple contact forms.
I'm assuming changing the submit button to a website link will require digging around in the PHP?

Yea, probably. I don't mess with the code.

[removed rival software info due to FB having the possibility to do what the OP asked for] is free. But 'if' you become a member and want unlimited use of ALL tools then it costs $5/mth or $24.95/yr. You do not have to pay a thing. Install the password protector and use it. If you get a high volume of traffic ( I'm not sure what the threshold is ) then they'll hit you up for the $5/mt. But set it up, try it out. Won't cost anything. If this site is for a client, they can create their own account and change the password as often as they like.

Thanks, Gunsmoke! I'm going to give it a try.

Isn't this basically what your looking to do.
http://progrower.coffeecup.com/forms/discount-code/
code is the regular expression. I can probably write you a script but this seems so easy.

That's exactly what I want to do!
I managed to make a simple form but haven't tried messing with the code for the submit button. In preview, the regex works but clicking submit opens a box:
JavaScript Alert
Submitted!


...If you know what you're doing.
I see you've not only got the submit button opening the URL, but the URL is hidden in the code. That's great!

I did nothing special. There's no scripts or anything. Just pure FB.
I setup the form with the reg expression required then set the confirmation up as a redirect to url back to this thread.
I guess you could show a link in the confirmation also but that's an extra step.

I don't have time now, but will have a look later and see if I can figure out how to " set the confirmation up as a redirect to url back to this thread."
I messed around with that a bit when I first tried it out, but couldn't get anything to work. Of course, I struggle with it every time just to get results sent to my email.