Custom Shop Items??

I'd like to change what my goblin merchant sells, as well as create my own shops. How do I go about doing this?

I spent some time messing with the Marketplace Actions but the dont seem to set the type of refreshing item like the gobline merchant...

sorry, was easier then I thought it would be!

For anyone else that doesn't know, just make a custom unit in the object editor and you can choose what it sells.