Extend/Change Recalculate Order button results

Hi there,

I'm looking at changing the Order Recalculate function because I added some fields both in the "Salesorder" Entity and "Salesorderdetail" Entity.

I've been investigating and debugging this and as far as I can tell:

1. The order calculation is not done in Javascript but in code, when I debug in the pre-processing step I do not see the calculated values in the attributes
2. If I do some recalculation and set the result fields myself, CRM overwrites my results. I tried this in pre-validation, pre-processing and post-processing with service.Update function.

Can someone tell me how I can get this working and where I'm missing something? I've been stuck with this since a few days and any help would be welcome.