I want to use a Custom Function to calculate the Sum of the Sales Orders with three criterias (Business Centre, Current month SO, and With another field selection). To do so, I am trying to do it getting the list of the sales orders under a Custom View I created and then sum them up..

But I am having some troubles getting there:

I tried with another Modules and did work, but with Sales Orders doesn´t. Is there any limitation with this Module? or is something missing in the way I am doing it?

All the help you can provide me, I´d be much appreciated.