Consolidate Invoice - Charge code

Hi Expert,

I am working on invoice consolidation.

Requirement:

While consolidate multiple SO into one invoice - there are charge code applied on each SO, While invoicing, I'll need to consider only one charge code.

Example:

Expected:

While Consolidate invoicing :  

100+200+300 + 10 = 610 USD [Expected result]

But standard would do: 100  + 200+ 300+10+10+10 = 630

Experts, Can you please give me hint, Where I will need to make changes to achieve above requirement.

Many thanks in advance.