validity Date of the Condition Record

Dear Experts,

I have to understand how system checks the validity of the condition record for the POs created before the condition record. For example, PO created on 1st Sept-2014 and Condition record (in MEK1) is created on 1st Oct, 2014 and PO pricing needs to be updated on 1st Oct. what is correct system behavior?

I am facing the issue that system does not determine the condition record during change in ME22N for POs which were created before condition record validity date.

Regards,

Hina