There are situations in which you may need
to link to or from a formula (calculated) field. For example, an employee ID
could be an 11 character value that consists of a two-character department code
followed by the employee's nine-character Social Security Number (for example,
HR555347487).
The formula language makes it easy to
extract the Social Security Number from this field:
{employee.EMPLOYEE ID} [-9 to -1]
- or -
{employee.EMPLOYEE ID} [3 to 12]
For the value HR555347487, either formula
would return the value 555347487.
While the return value is a valid Social
Security Number, the fact that it comes from a formula prevents you from using
the field to link to a Social Security Number field in another table. You can
report on and coordinate the values in the two tables, however, by using a
subreport.