From email to shared hosted backend to remote frontend

So my friend hosts a little get together every once in a while where space is limited to the first 14 people who RSVP. He emails the invite out to a list and then accepts the first people who respond. Tonight I barely got in because I can't always check my email, so I told him that I would write a program that would respond instantly to his request. This would not normally be a problem (autoresponder, easy) except he has recently created an online signup form. I think it would be funny for him to send out his next invite and get a sub-100ms response from me, so I would like to give this a try.

The problem is, I'm not quite sure how to go about it without going to to much expense. I have a personal site that can host some .NET backend code, but it's on a shared GoDaddy server so I don't really have a ton of access to the mailserver or anything. I was thinking that if I could get an email sent to a certain address that maybe it could trigger a webrequest that could pull down his page and then fill the (very simple, like 2 or 3 inputs) form out and submit it, but again, I'm not quite sure how.

Would anyone have an idea about how I could go about this? I would want for this to happen automatically without any sort of interaction from me, just basically as soon as I get an email from a certain email address, somehow my code is triggered and the form filled out and submitted.

This is just for fun, but the programmer in me is curious as to how I could actually get this to work.

Thanks!

The most affordable thing I know of would be through NearlyFreeSpeech.NET. If you set up an account there, you can configure a domain with email forwarding for 3 cents/day. They have an option to forward the email to a script, so you could write something that would look at the mail, pull down the form, and post to a server.

I'm not sure but I think the script has to be running on their servers, so you'll have to set up a website (another few cents per day) and write the script to run in a UNIX environment (PHP or Perl or such). If you insist on .NET, you could write a minimal PHP script to forward the data to your GoDaddy account.