/MARK_CHANGE
       /NOMARK_CHANGE (default)

    Controls whether the lines that change in a DO display each time
    it is automatically updated are marked. Not applicable to other
    kinds of displays.

    When you use /MARK_CHANGE, any lines in which some contents
    have changed since the last time the display was updated are
    highlighted in reverse video. This qualifier is particularly
    useful when you want any variables in an automatically updated
    display to be highlighted when they change.

    The /NOMARK_CHANGE qualifier (default) specifies that any lines
    that change in DO displays are not to be marked. This qualifier
    cancels the effect of a previous /MARK_CHANGE on the specified
    display.