Hi Shreder,
While there are a couple ways of accomplishing this, you should definitely check out the Dave Brown Fiberglass Pushrod system. It has fittings that allow a "Y" pushrod arrangement, which is perfect for single-servo, dual elevator set-ups. Just as it sounds, you'll have one wire on the servo end of the pushrod, and two wires coming out of the control surface side.
Go to the DB website, then "Order/View Products", and scroll down to the bottom of the page to find them. While not exactly cheap, they are well worth it. [sm=shades_smile.gif]
http://www.dbproducts.com/
I'm sure others will chime in with other methods, but I found this to be the best system for what you're trying to accomplish.
Hope this helps!