Substituting sweetened condensed milk for evaporated milk
The main difference between the two products is that sweetened condensed milk has added sugar.  This could be a problem for your recipe.  Evaporated milk, since it is concentrated (about 60% of the water is removed) is already a bit sweeter. When sweetened condensed milk is made, more sugar is added to evaporated milk, leaving the final product in the 40 - 45% sugar range.  So, the answer to your question will, in large part, depend on your recipe.  There are caramel recipes online that make use of sweetened condensed milk.  You might just start off with one of those.