If the sugar is to be either pulsed or melted, does it need to be superfine sugar?
This is a good resource that might help: http://www.slashfood.com/2006/05/23/sugar-vs-powdered-sugar-vs-superfine-sugar/
You can sub regular sugar in the portion you are cooking - just make sure it all dissolves. I wouldn't sub it for the powdered sugar in the crust.
I use superfine sugar out of habit when making caramel or candies...that is why I called for it...it melts so much easier without having to worry about a grainy texture.