I'm really craving some No Bake cookies right now, but I don't have any cocoa powder or unsweetened baking chocolate or chocolate chips. I do have a Hershey's candy bar though (1.55 ounce). I was wondering if I could substitute the chocolate bar for the cocoa powder if I reduce some of the sugar in the recipe. The recipe I have is:

2 cups sugar
1 stick butter
1/2 cup milk
1/4 cup baking cocoa

Mix these together over low/med heat, stirring until combined. Bring to a low boil, and continue boiling for 2 MINUTES EXACTLY

Remove from heat add:
1/2 cup peanut butter
1 tsp vanilla
3 cups quick oats

Quickly combine and spoon onto wax paper.

So, can I use the candy bar instead of the cocoa? And if so, how much sugar will I need to take out?

Thanks in advance!