Good Receipt against Scheduling Agreement

Hi,

I have created Scheduling Agreement and maintained delivery Schedule.

No while making Good Receipt against scheduling agreement, system give message that no item exist.

I have given date in delivery schedule for e.g 27.06.2008 and I am entering good receipt on 26.06.2008. But it is not possible.

Once I change the date to 26.06.2008 in delivery schedule, then system allow to post a good receipt.

Why, Is there any setting to remove this?

Waiting for your reply.

Thanks,

Samir Bhatt