I have tried several different recipes for cream cheese icing my self and have had alot of luck with this one.

4 ounces Margarine or Butter
8 ounces Cream cheese
1 pound Powdered sugar

You can add a little extra powdered sugar if you like to make it a little more stiff. It does get sticky if left in the heat too long but I have never had a problem with it running. A little clear piping gel added to this makes it easier to pipe with. Hope this helps!