postBlock                                    (Assignable)

        Contains an optional code block that validates a newly entered value.
        If present, the Get:postBlock should contain an expression that
        evaluates to true (.T.) for a legal value and false (.F.) for an
        illegal value.  For Get objects created with the standard
        @...GET...VALID command, Get:postBlock is assigned the expression
        specified in the VALID clause.

        The Get object itself ignores this variable.  It is used by the
        standard READ command to implement the VALID clause.

        During postvalidation the Get:postBlock is passed a reference to the
        current Get object as an argument.  Note that this differs from the
        CA-Clipper 5.0 behavior where the Get:postBlock was passed the
        updated value of the GET variable, and a logical value representing
        whether the Get object had been edited.