Library /sys$common/syshlp/dbg$help.hlb DEBUG, Built in Symbols, %NEXTSOURCE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Specifies the next source display after the current source
    display in the screen-mode display list. The current source
    display is the display which receives the output from TYPE and
    EXAMINE/SOURCE commands.

    Example:

    DBG> SELECT/SOURCE %NEXTSOURCE