Hi, ourjewel. Welcome to Discuss Cooking, you'll like it here.
My experience with Splenda is that it won't work in situations where the sugar you are replacing is expected to do something more than sweeten, as with candy. When making candy, cooking the sugar causes it to thicken and give a harder candy the hotter you make it. I don't think that will work with Splenda. I tried to make simple syrup with it once and it didn't work at all.
Hang in there, someone with more candy knowledge will be along before long to offer more info.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan