I can't seem to get this to work. I need to add a field 'discount' to an invoice where it returns "-20.00" when certain criteria is met. Customers will get a £20.00 discount if they pay within 62 days, but only applies to sales from 1/10/15. So the date in 'Invoice Date' must be from 01/10/2015 AND the day count in 'days' must be between 1-62 days. I also would like the 'discount' field left blank if the 'payment date' field is blank.
The 'payment date' field is used to calculate the 'days' field. The sum works out number of days from the 'Invoice date' date subtracted by the 'payment date' field.
I hope this makes some sense.
Thank you in advance.