Hi my script goes like this.

gzcat Jan06.gz | awk 'BEGIN { FS = "|" } ; $2 ~ /^[A-Z]{3}$/ { print $2 }' > cnt

sort -n cnt | uniq -c | sort -n > cnt1

cat cnt1 | awk 'BEGIN{OFS="|"} {print $1,$2}' > rep

here i am hard coded Jan06.gz .
but it is inside the dir /gns/gnsadm/notify/bpdcc/work/
every day new file will be generated (ex Jan07,jan08)

how to do in generic manner?

To run the script using the most recently modified file in the directory:

LATESTFILE=`ls -t /path/to/directory | head -1`
gzcat $LATESTFILE | ...

What you have said is correct. But other files are also there.
So based on the format is there any way?

Usually file is generated like this

Jan05.gz, Jan06.gz

rgds
s.kalyan

/bin/date can take arguments to format the output and generate the filename. Something like

FILENAME=$(date +%b%d)

should work, but check the man pages.