Caramel cake icing

This is Ray's favorite cake, and an old family favorite, but it's incredibly hard to make and have it come out right. The one we made for his birthday (Christmas day) turned out great...so here we go at trying to duplicate the recipe.

2 cups of sugar
1 can of evaporated milk
1 1/4 stick of butter

Blend in pot, stirring constantly, until boiling for quite a while and at the same time, in an iron skillet melt 1 cup of sugar. Combine the two and cook until soft ball stage. Remove from heat and use mixer to beat it while it cools. Poor onto cake. :) Watch for dribblies off the side and just put them back on top. Caramel should harden and become smooth.