Elevator control

Hi there

I am quite familiar with siemens s7 200 and s7300.
I am getting a little stuck in an elevator control circuit.

Is there an easier way of creating memory for the lift so that it knows it must stop on a floor and carry on to the next requested floor.

I have managed to do this in relay logic but it is a little cumberson.
I have tried using shift registers,but to no avail


Please somebody help

u can use a first in first out table
add requests in a table and each time the elevator stops , the fifo table will show the next destination