Caster sugar but need icing sugar

[HiccupHaddockHorrendous]

I have a vague idea that I can use my stick blender to make caster sugar finer...is that right? Or will it not matter too much if I just caster sugar as it is?

You can blend it up, that will make it finer.

What is the icing sugar for? Caster sugar will not work as a substitute for some things (like icing!)

It's for a waffle recipe.

It also needs melted butter so could I melt the sugar into that?