Mailing to Multiple Recipients

Hey, I need to create a script that will e-mail the out put of a form to multiple people (upwards of 100 at a time) I am going to use <select multiple> <option value=email.address1@somewhere.com>Name</option> <option value=email.address2@somewhere.com>Name</option> <option value=email.address3@somewhere.com>Name</option> <option value=email.address4@somewhere.com>Name</option> </select> So that a user can select all or some or all of the addresses. I also need to add some function for the suer being able to choose whether to use his own text or a pre-written message. I am not sure how to go about doing this. I have done some simple mail() stuff but nothing substantial. Your suggestions would be very appreciated!! Jeremy