Authenticate issue

I am using a basic flat file for password authentication for my internal users. Depending on the pin number they enter, they can dial externally or not. However, i am also using a small php web page to enter, edit and delete the pin numbers. This writes two pieces of information (username & pin number) as follows in a flat file, note the “|” delimiter,

1234|user1
5678|user2

etc.

Is there any way using the authenticate command to read just the four digits at the beginning of each line to use as the pin numbers? At the moment i get password incorrect, no matter what delimiter i use. Any help much appreciated. I am using asterisk v1.2 with an X-Lite soft phone.
I have searched the boards and the authenticate examples, but have found no luck extracting JUST the pin number from a file containing user names as well.