Grouping Taxable/Non-Taxable amounts in PLD

Hi,

How can you group in PLD the amounts of taxable and non-taxable VAT codes? I mean if I have for example 3 kinds of VAT codes in the system which are 0 rated, and 3 kinds which have different rates and I would like to summarize the row amounts by: 1. sum of amounts of taxable VAT codes (codes where rate greater than 0); 2. sum of amounts of non-taxable VAT codes (codes where rate = 0)?

Thanks in advance!