Thank you very much sir for helping.

But now I need your more kind help

I have added a new field called max_qty where I want to put 1 against maximum qty in every idid group.
Like shown in attached image

CREATE CURSOR junk(qty n(3),idid n(3),max_qty n(3))

INSERT INTO junk values(5,1,0)
INSERT INTO junk values(10,0,0)
INSERT INTO junk values(15,0,0)
INSERT INTO junk values(20,0,0)
INSERT INTO junk values(25,0,0)
INSERT INTO junk values(30,0,1)
INSERT INTO junk values(15,0,0)
INSERT INTO junk values(10,0,0)
INSERT INTO junk values(5,0,0)
INSERT INTO junk values(0,0,0)
INSERT INTO junk values(10,0,0)
INSERT INTO junk values(15,0,0)
INSERT INTO junk values(20,0,0)
INSERT INTO junk values(25,0,1)
INSERT INTO junk values(20,0,0)
INSERT INTO junk values(15,0,0)
INSERT INTO junk values(10,0,0)
INSERT INTO junk values(5,0,0)
INSERT INTO junk values(10,0,0)
INSERT INTO junk values(15,0,0)
INSERT INTO junk values(20,0,0)
INSERT INTO junk values(25,0,0)
INSERT INTO junk values(30,0,1)
INSERT INTO junk values(15,0,0)
INSERT INTO junk values(10,0,0)
INSERT INTO junk values(5,0,0)

Sir I modified as

* Get our first value
GOTO top
llGoingUp  = .t.
lnId       = 1
lnLastQty  = qty
SCAN
    IF llGoingUp
        IF qty < lnLastQty
            llGoingUp = !llGoingUp
        ENDIF
    ELSE
        IF qty > lnLastQty
	         REPLACE max_qty WITH 1 && I wrote this line but it displays 2 max_qty in last group
            lnId      = lnId + 1
            llGoingUp = !llGoingUp
        ENDIF
    ENDIF
    REPLACE idid WITH lnId
     
    lnLastQty = qty
ENDSCAN

BROWSE LAST

Please help