How to avoid planned orders during future shutdown time in Manufac Plant

Hi,

Our one manufacturing facility is planning a shutdown starting from 12/20/2011 through 01/05/2012. The plan is to start up production by 01/06/2012. The calendar has been closed using CR02. However we still have planned orders inside the period.

After checking, we found the Planned orders were created by APO Heuristic. and shutdown duration setting in downtime of Resource does not work if there is demand.

How to avoid having planned orders during the shutdown time in APO Heuristic?

Thanks

Su