Complex Form with formmailer

I tried for quite a while now to include a complex form for online subsriptions to special lessons/courses.

I have the normal contact-from plugin installed and it works fine.

However when I try to make a complexer form work I just can’t get it to run. What I do is create the form code in .php file and define it as template. Then call it from a new page without entering any content. That works fine just the actual method of posting/sending the mail doesn’t work.
I tried php formscripts, and cgi ones. Is there any special rule I have to follow in order to make it work?

Does someone have a complex form which is working under wordpress and which I could work from?

Thanks in advance.