Hi,
There are a few ways to accomplish this:
1) Have a look at the Scheduled Task Adapter from Codeplex:
http://biztalkscheduledtask.codeplex.com/
2) Build a task in Windows Scheduler to copy an XML file into your receive location to launch your orchestration.
3) Use a third-party job scheduling software to handle that task.
I hope this helps. Good luck!
Daniel.