In a composed string, if the field can contain a numeric field-value then you may use an arithmetic expression in place of a field-name. These operators may be used:
+ to add,
- to subtract,
* to multiply,
/ to divide (rounding towards zero),
\ to provide the remainder after division (the mod function)
and use round brackets () to contain intermediate calculations.
to check whether the current page number supplied by a field named pagenum is odd (when remainder is 1) or even (remainder is 0).
where field1, field2 and field3 all supply numeric values.