/sys$common/syshlp/helplib.hlb CC, Messages, NEEDARITH  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Message        <Context> "<expression>" has <type> type, which is
                not arithmetic.

 Description    An expression that must be an arithmetic type was not
                an arithmetic type.  For example, the operands of an
                arithmetic operator such as * must be arithmetic
                type.

 User Action    Modify the expression so that it is an arithmetic
                type.