JBA ML - Use of Discount Lists for Promotional Periods

We are currently experiencing difficulties with the use of Discount Lists.

The situation we face is that we have upto 4 day's transit time for products
to customers.  We also run promotions with discounts which are based on the
days the customer receives product.   For example a 10% discount may be
applicable from Monday which is then applied to approx 10% of customers
orders despatched on Friday, 30% of customers orders despatched on Saturday
and 100% of customers orders despatched on Monday.

We can't accurately use the discount lists as they apply the discount based
on the date the customer places the order.   Does any one out there have a
similar situation and if so how do they manage it.

Thanks in advance for any ideas.

Patrick Mullen
System Development Manager
Mrs Crocket's