My problem is is that those 4 fields are all calculation fields, so i can not modify them with this script step...
... but you can modify their calc !
I run the scipt and a box pops up that says "this action can not be performed because this field is not modifiable."
A calculation field can be modified only by its calc.
So you only need to add a Case statment to their calc.
Can you please give me an example of the case statement that i should put in the calc?
I do not know the actual calculation but, as an example let it be:
To have it 0, it could be:
invoiceitem = "shipping" ; 0 ;