Different level elevators

All I want is to be able to have a stand-alone building that's 2 floors high while the main building is 4 floors high so the elevator only goes to 2 FLOORS and not to 4 FLOORS. right now if I want to have a 2 story building I have to connect it to the 4 story building so they employees can access the upper levels when i try and put an elevator in the 2 story building it just goes up 4 floors and when I try and delete the top 2 floors the elevator disappears it's kinda annoying

I'm not sure where the problem is occurring. You want a four storey building with a four storey elevator and a two storey building with a two storey elevator that connects to the four storey building, correct?

Dynamite the third and fourth storey floors on the two storey building. After that, it will only add 'new floor' to the four storey building.