Solved it. Used an calculated column for list setting in SharePoint. Case closed
This is the scenario
I would like to calculate column =[Omsetning]*[Sansynlighet]
But I receive an Error "Validation formula can refere to this column, and no one else". Translated from Norwegian. And a second thing. Only . is allowed as decimal separator, and not , (comma) which we use her.
I Migth be using the wrong Item in the column values. The Header says "Column validation".