Liquadation / Promotional Qty across all orders for a item / item category in a specific period

Dear Team,

Please let me know the requirement as per below

1. For a specific Item we need to provide Liquadation / Promotion Pricing for a qty of 1248 pcs for a specific period say till 31-May-16

2. These orders will be raised in Oracle in stages today 200 , tomorrow 200 etc... and not in one stretch

3. After the 31-MAY-16 the normal rates will get applied

The Qty should not get exceed 1248 pcs across all orders for a specific period for a set of customers

Regards

sriram