Know-How Exchange : Other

Does anyone know of a company that will do a direct mailing of a letter with a "key" inclosed for the consumer to bring in to see if it fits in the lock for a chance to win $1M? (the promo would obviously need to be insured) I've seen this used for grand openings...and car dealers have done something similar to win a car. Any other ideas along these lines would also be helpful...I'm trying to come up with a really exciting re-grand opening promotion of our credit union (the building was destroyed in a hurricane and we've been in limbo for two years now-so I want to really thank the members for hanging in there with us). Thanks.