Program BVALID.PRG illustrates how to use the VALID clause with the BROWSE command. The VALID clause is evaluated when you move from record to record. In this example, the letters ":F" is placed after the VALID keyword (VALID:F SHOWPOP()) to force the validation even if you do not change any fields in the current record. In Program BVALID.PRG, the VALID clause calls the SHOWPOP() UDF whenever you move from one record to another to display the 1980 population in a window. CENSUS.DBF contains 1989 population for each state.
