[TYPO3-shop] customers + VAT - Resellers no VAT

[Simon Justesen]

Hi,

I'm having a bit of a problem with a shop

With normal customers - prices are entered into the database with added 
25% Danish VAT.

So the calculation, like normal tt_product behaviour is (I think):

SUBTOTAL (incl. VAT)
VAT ONLY AMOUNT
+ SHIPPING
= TOTAL


Reseller prices are entered into the db ex. VAT to make it easier for 
the backend user
I need to have the subtotal behave differently, like this:

SUBTOTAL (ex. vat)
+ VAT
+ SHIPPING
= TOTAL

How's this done? I've been playing around with
plugin.tt_products.TAXpercentage = 25.00
plugin.tt_products.TAXmode = 1
plugin.tt_products.TAXincluded = 0

But can't really get the correct results.
Would I need to change the source or do you have a TS workaround?

Thanks,
Simon