Scheduling in production order

Dear all hi,

I have a production order which takes 5 working days to complete the production qty of 10 units.

When i select the forward scheduling & enter the start date 01.01.2008, then the system is correctly calculating the basic finish date as 06.01.2008.

but when i select backwards & enter the basic finish date as today 28.12.2007, the system is scheduling the basic start date as today but not scheduling backwards as i require it to be 23.12.2008

please help.

Thanks in advance.