I can't help you with the recipe BUT I will share a secret with you. A friend of mine turned me on to this .... drop a piemento stuffed green olive in your Marg! HONEST!! I'm talking about the regular Marg - not the "frozen" ones - the real one with salt around the rim. The sourness/saltiness of the Marg goes perfect with the Olive, and the Olive is SO YUMMY when it's been drinking for a while!!!
Last year at a resort in Jamaica I was drinking them. This year when I went back, the bar tender (who we became friends with, and remain friends with) is now serving Marg's with Olives "Sue style". Said his customers think he's nuts at first, then they try them and they're amazed.