How to make WinSCP wait until previous WinSCP call is completed?

Hi there,
I have a AZ.bat file within which WinSCP.exe line is executed for file transfer(move). This AZ.bat is triggered automatically from a scheduler. Issue is the scheduler triggers AZ.bat more than one time simultaneously, this is locking the files from being accessed. So how can we make either AZ.bat file or the WinSCP to wait until previous or the before call is completed? Any ideas will he really helpful.
Thanks.

The Task Scheduler has an option "If the task is already running, then the following rule applies" with an option "Do not start new instance" – It's actually the default value.