Tier calculation for volume offers

Hi All,

We have a typical scenario wherein we need to alter the tier calculation for our volume offers. For e.g.

Tiers defined with retro flag as Y:

1 - 10 - $20 per pc

10 - 20 - $30 per pc

20 - 30 - $40 per pc

Items included:

A

B

C

Orders placed by eligible customer:

Order 1: Item A - 3 pcs

Order 2: Item B - 10 pcs

Under normal circumstances, customer will fall under Tier2 10 - 20 as they bought 13 in all and we will accrue 13 * 30 = $390.

Item A and B are essentially same products but different sizes by volume. So 10 pcs of item B are essentially equal to 5 pcs of item A by volume. When we do the tier calculation, we need to consider item B as 5 pcs and calculate the tier as 3 + 5 and accrue under Tier1 i.e. $20 per pc with total accrual amount as 13*20 = $260.