That's way beyond the scope of InDesign. You'd have to ask in the Acrobat forum.
On a side note, though, there is a licensing limit to the total number of forms that can be returned by email, and I believe that number is 500, without purchasing a Live Cycle license that would probably allow you to run server side scripts to take care of the count.
Personally, I would have the form be a fill-out, print and snail-mail or fax form. Have the URL on the form for people to go to an on-line version of the form.
Emailing forms or form data can be fraught with problems. So many people these days use something other than what would be considered a "default email" application. Instead opting for browser-based emailing.
You can have a button that pushes people to a web site for on-line registrations. Use PHP or ASP.net to process the form. Have a simple shopping cart system to deal with quantities of registrations for any given event.
You can have the Acrobat form data feed a PayPal shopping basket upon a submit action as well. Depending on how you set up the PP account, it can keep simple "inventory" (in your case, seats at an event) so you cannot overbook.
But using Acro forms for such direct "booking" isn't something I recommend. Once people click that submit butting, whether they are sending XML or whatever data type vial email, or simply pushing them to an on-line form, they will get a security warning about whether they really want to do whichever action you've scripted.
Just my opinion about "live" Acro forms.
Take care, Mike
Well, there isnt any payment involved, but thanks for the reply's. think im gonna use the php registration form idea.
You dont happen to have a script lying around?
Not any handy. Your ISP may have a PHP forms processor already on your system available from the control panel.
There are a couple form builders I can recommend. One is Forms to Go. I believe Coffee Cup also has a builder. FtG works well and can be reasonably integrated in an existing or now HTML page. I also believe the PHP processor is included.
Take care, Mike