Which UI Prototype tool should I use?

I have been searching for UI prototype tools which enables me to implement code logic, along with decent UI features. In one project, I would like to be able to implement a drop down list which the user picks a choice, which can affect the list of choices shown by another drop down list. Mind me, I am fairly new to UI/UX design and web design. And no, I would not like to use HTML due to its inflexibility and it being difficult to modify/extend. Any suggestion of good UI tools, whether be it free or paid?