Library /sys$common/syshlp/decset$envmgr.hlb cgui, symdef PopForm, def TxtF  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Type a new (or edit an existing) symbol assignment in this field.
    The assignment associated with the selected symbol definition is
    displayed in this field.  Use this field in conjunction with the
    Enter Define and Replace Define buttons to add or change symbol
    definitions in the Symbol Definitions list.