Programming :: Inserting Usr Into /etc/passwd Via Script?

I need to either locate a script that is similar to what I am needing or figure out a better way of doing what I need. I have mutiple shops with AIX unix servers, using ksh with virtual terminals that connect. since these are on an internal network we have them connecting to the server as either usr01, usr02, etc. what I need to do is add 15 user's ranging from usr01-usr15 into /etc/passwd each usr is identical in such that each line contains

Code:

usr01::0:0::/usr/tops:/bin/ksh

only difference is the usr# changes. I wrote a script where I was just adding these all to the /etc/passwd but now I have been tasked with adding them to these shops but with out any duplicates. is there any way to have a script check the file to see if the usr# exists and if so proceed to the next number and then input the usr#::0:0::/usr/tops:/bin/ksh into the file?