BDC session error handling for IW41 transaction

Hi,

When the order confirmation is done by BDC session program, it is executed without any error. But if we do the same process manually, it is showing the error message as 'Posting period is Locked for 001 2012'. My question here is why this is not happening when it is executed through bdc session program.

Anyone can help us?

Thanks,

Guna