Reference Fields and Reference Tables
You must specify a reference table for fields containing quantities (data type QUAN) or currency amounts (data type CURR).
This reference table must contain a field with the format for the currency key (data type CUKY) or unit of measure (data type UNIT). This field is called the reference field of the output field. The reference field can also reside in the table itself.
A field is only assigned to the reference field at program runtime. For example, if a field is filled with currency amounts, the corresponding currency is determined from the assigned reference field, that is the value entered in this field at the moment defines the currency.
Table SBOOK in the