Question 'Frame-Line' displaying 0 for every line in a scrolling frame

[Prashant]

Hi,

I have to add a trigger in 'Schedule Maintenance' (5.5.3.3) on Quantity field in frame 'Schedule Detail Data'.
For that I need to know on which Frame-Line I am working.
So I wrote this query:

{mfdeclre.i}
ON GO,LEAVE,ENTRY ANYWHERE
DO:
IF FRAME-NAME = "sched_det" and frame-field = "schd_upd_qty" THEN
DO:
DISP FRAME-LINE.
end.
end.
{gprun.i ""rssmt.p""}

but when I am executing this query I am getting Frame-Line 0 for every line.
I looked into the core program rssmtb.p (called program of rssmt.p) and they have used Frame-Line function for this frame, then why it is not working for me?
Can anyone please help?