Anyone know how to accomplish two actions with one form?

I'd like a box allowing users to, say, sign up for an e-magazine from getresponse.com AND sign up for a newletter from Topica.com all with one submit button.

(I'm using their html scripts linking to their CGI. I don't have access to CGI.)

Any way to allow users to check a box self selecting which of the two they are signing up for?

Possible?

Thanks ahead of time for any help you guys can give!