Subfile API QdtsSetDspAtrSF - Set subfile display attributes

I'm trying to develop an utility to edit the contents of a data area and the
layout of this utility's screen would be similar to DSPDTAARA screen, but
with an editable field. If the length of the data area is not divisible by
50, then I need protect (and nondisplay) the remaining extra length of the
last record displayed on the subfile.

To do this, I tried using QdtsSetDspAtrSF API but I'm getting a value of -1
in the return code, which means "record not found". My RRN value is correct
and the record is present but I'm not sure why Iam getting this error. I
tried to refer to some examples of this API but unfortunately I couldn't
find anything via google. If anyone has a working example of this API,
please share it with me. I have also used QdtsInitSF to initialize the user
space in QTEMP in my *INZST subroutine and I can see the userspace in QTEMP.


Here is my logic,

DOW loop to write records into the subfile.
1) Increment RRN by 1
2) If it is the last record, then call API QdtsSetDspAtrSF to protect and
nondisplay the remaining area of the subfile field.
3) Write Subfile
ENDDO


I have also tried to write the subfile record first for the particular RRN
before calling the API (interchanging step 2 & 3) and still it didn't work.

Thanks in advance.