Creating forms in flash

I’m trying to create an order form of sorts. I am a photographer and I would like to have my clients fill out an online form and have it email to me. I know the basics of creating a form and I think I can do most of it. I would like to have a drop down list of all of the different sizes of prints we offer, when a client selects one say and 8 x 10 it will fill in a predefined price for that size. The other item I dont know how to do is create a total. When they fill in all of the sizes I would like to have an update button that totals all of the rows together. I would also like to have a button to add another row of drop downs. So it would start with 5 rows of drops downs for different picture sizes then when they click “Add Row” it will give them another dropdown to add to the list. I hope all of these questions make sense. If someone could point me to some tutorials or something to help out that would be great. Thanks in advance for the help.