Batch Search Determination

Hi,

We have a product which is set up with a shelf life of a 100 days. When we book it in and enter the production date, the material, which is assigned to a class containing Expiration date, shelf life characteristic, this gets populated. This is working fine.

From the customer view, some customer requests that from the delivered date, the product has to have a min of 50 days shelf life. Can anyone help me on setting up this logic...

Thanks in advance,

Finbarr