Condensed milk is Not the same as Sweetened Condensed Milk <<< You need a can of this. And yes it works. If you do not have a crock pot you can also do this by putting the can, un-opened, in a kettle of water, bring to a boil, reduce heat and simmer for ?x? Hours, adding more water periodically to keep above the can-line.
I think you can also open a can of Carnation Sweetened Condensed Milk and pour into a kettle. I do not know the method to cook it this way.
Maybe a double boiler?
You may also ask a large grocer to order some Carnation Dulce de Leche. I have seen it already made in Mexican/ Latin grocery stores here.