I tried googling but found nothing so I just ask here. Is it possible to bind my mouse 3 to hotbar 2?

Currently I need to use ctrl+1 to use first skill in horbar 2 but I would like to change it as mouse3+1. I tried that ingame but I could not figure how to do it and it seems that it is not even possible. Can anyone tell me how to do it or if it really is impossible in which case I need to buy new mouse which has more buttons to bind for ctrl etc.