Can I substitute granulated sugar for caster sugar in Marzipan? I'd like to make marzipan, but I don't have caster/superfine sugar, only &quot;regular&quot; white sugar. Will it work, or are there any tricks to make it work without a grinding implement?

I just finished a batch after using a blender to grind up the sugar (the almond was already in powder form). The consistency might be a bit coarser, but I'm not sure I can tell the difference.
No, you can't do it. Marzipan has a smooth paste consistency. Granulated sugar is not suitable, you'd end up with a preferred mixture of sugar and ... almond crumbs? Without a grinding implement, you couldn't reduce the almonds to the needed consistency either.