If (Production Paid By = "Gallery" AND Production CURRENCY = "£" ; Production Cost)
thank you. How does & differ to AND exactly?
They are completely different.
& is the concatenation operator. It "Glues" two strings of text together to make one string. "ABC" & "XYZ" ----> "ABCXYZ"
AND is a logical operator. If you have two Boolean expressions such as Production Paid By = "Gallery"; Production CURRENCY = "£" , by putting "And" between them you get a result of True only if both of these expressions also return True. If either evaluates as False, your result for the entire expression also will be False.