Contests & your website

Sorry for the duplication - wanted marketing & technical input if possible:

We are looking at running a contest where the purchase of three productions automatically enters you into a draw for a trip to England. However we need to also provide a 'no purchase necessary' part to the contest to satisfy legal.

Have any of you created something for your website that ties into Tessitura (contact info, original source and/or CSI) that also provides the ability to ask a skill-testing question and ultimately a 'You are entered into the contest' or a 'Please try again' response to the question?

Have you worked with an outside provider to gather that information? What companies did you work with and would you again?

Any help would be appreciated.

Michele