Sorry...I probably shouldn't have posted this in the Contact Form 7 forum, as the drop down menu in question pertains to the Paypal button not Contact Form 7.
However, I'm using a Contact Form 7 form and pasting the Paypal button in the "# Sender's message was sent successfully" message after someone finishes the form correctly and clicks submit, so that the payment option appears only after the form is submitted. This works well if I don't have a customized Paypal button with the drop down menu for price selection (if you make a simple button you get the option to copy an email code rather than the html, which is what works on WordPress sites.)
So as more relevant question to this forum: can drop down menus in Contact Form 7 trigger the appearance of new fields depending on the selection? Or maybe if the first question is membership type (which would indicate the particular cost of membership) could a new page automatically load where the form could be completed and the appropriate paypal button (without price options) would appear at the bottom?
Thanks for any help anyone can offer.