Sorting Parameter LM LY VS LM CY

HELLO I WANT TO USE PARAMETER AND HAVE LEGEND SORTED LM LY (LAST MONTH LAST YEAR) AND THEN LM CY ( LAST MONTH CURRENT YEAR) AND  DATA ON THE GRAPH BY BIGGEST QTY/AMT LM CY FIRST. EACH TIME i CHANGE AMT TO QTY SORTING ALSO CHANGES AND IT SORT BIGGEST AMT/QTY LM LY WHEN I WANT TO HAVE IT LM CY.