i m working with messung system plc,,,,,,,,need some help........

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hi there ,,,,,,,,any body plz help me out,,,,,
anybody knows about messung plcs?????
i m working with one of it in my project,,,,,,myself is doing a project of plz based elevator model,,,,,,the model has 4 floors including ground floor.......in this model i m sucsessful in moving the elevator cabinet up n down as per call push buttons,,,,,,
but the problem i m getting is as follows..................................

consider the elevator cabinet is at 3rd floor ,n i push call push button of 1st floor,and immediatly after that somebody calls from ground floor,,,,,then cabinet should 1st stop on 1st floor n then go to ground automatically,,,,,right?
for this ground call should be latched untill call from 1st floor (1st operation)is over......and there should be some delay or cabinet should stop at 1srt floor for sometime so that person at 1st floor
could enter in it......
now my probleeeeeemmmmmmm
how to latch one input with required time delay using this plz model xmp820 of messung plc?????n i have dox-mini software (ladder progrmming).....