Restricting Multiple Entries on a Form

[curtiss]

I'm developing quite a few forms here at work, and I keep running up against one particular problem that pretty much has me baffled. I am asking for advice and suggestions from you guys.

When I develop a new form, in most cases, I want to be able to stop someone from being able to submit the form more than once. Tracking IP addresses is pretty much out of the question, since so many of the respondents will all share IP addresses.

I have thought about using cookies to stop someone from submitting the form multiple times. In some cases, this will work. However, in other cases, I'm not really looking to stop them from submitting the form more than once, I'm just trying to stop them from submitting the same information more than once.

For instance, one of the forms is an RSVP form, allowing users to tell us whether or not they'll be attending special events at the College. Obviously, some users will need to submit the form more than once, as they very well may attend multiple events. However, I still need to find a way to successfully stop them from accidentally responding more than once for the same event.

In most cases, I have just set up my forms to check the database to make sure there are no other entries with exactly the same information. However, if someone inputs slightly different information the second time around, the processor won't catch this.

For instance, if I submit the form using "Curtiss Grymala" the first time, but I submit it using "Curtiss A. Grymala" the second time, both submissions will go through successfully.

Any suggestions?

BTW - All of the forms in question are currently written in VBScript (not VB.Net) and dump into an Access database.

[Allen]

Is email or name on the field list typically?

You could do an ajax/button lookup - and if x email address is already on the list, stop them.

So one idea is:
-- instead of showing the whole form, just show email address field
-- they input email address, click verify
-- if not in, ajax display the form
-- if in, show error message

[Deadeye]

you can also check via ajax or on submit, and parse the name (via spaces) and do a regular expression or a name like '%Name%' and check for the same subject or event. If you match (2 first name/last name) out of 3 or more (middle initial) than you have the same persion.

Hope this helps

Wesley