Billing split: create split by TAX code

Hey Guys,

we are trying to implement a split criteria for invoices:

If the items selected for billing have different TAX codes, then the invoice should be split (1 Invoice per TAX code).

How can we define the Tax code of the items?

I know the Konditions in KONP via A002 & A011 are used, but as SAP is doing it anyway, which program/function module can we use to return the Tax code and use it as split criteria?

I hope we do not have to recode the logic!?

We are stuck on thsi topic - PLEASE ADVICE!

Thanks,
TIM