Try:

REPLACE MyField WITH lcSomeValue IN MyDBF

>First time for this:
>Changes to a combo setting push a message to user offering to replace the contents of a "Master" DBF field.
>
>When the code instructs:
>replace MyDBF.MyField with lcSomeValue - it does not take.
>
>However, when code instructs:
>select MyDBF
>replace MyField with lcSomeValue - it takes.
>
>It's one little interactive procedure. A form deactivate fires a "custom" data session object in service of a MESSAGEBOX just before the REPLACE. Maybe some foobar character codes hidden in the PRG file. Just weeeeerd.
>
>The "->" field pointer has same non-result.