Agilent Technologies 8566B Operating And Programming Manual page 354

The MKPK command positions on the active marker on signal peaks.
OUTPUT 718;"MXPK NR;"
Executing MKPK HI, or simply MKPK, positions the active marker at the highest signal detected.
If an active marker is onscreen, NH, NR, and NL move the marker accordingly:
Specifying NH moves the active marker to the next signal peak of lower amplitude.
Specifying NR moves the active marker to the next signal peak of higher frequency.
Specifying NL moves the active marker to the next signal peak of lower frequency.
(See also KSK and El .)
MKPK
Marker Peak
Programming 245