You'll have to be really, Really, REALLY careful with the CGI script and have some way to make sure that you are the only one who's allowed to relay mail. Otherwise it'll be an open relay just waiting to be abused. Since your workstation is on a modem connection I imagine that you get a new IP assigned every time you log on, so you've got to figure out another way to restrict access than checking the address of the client.

Anyway, good luck. (Personally, I'd consider getting a web mail account or similar and do without all the hassle)

Cheers,
-- moodster