Jmeter: wants the script to use unique value

Hi all,
I have installed the jmeter and created a script and recorded the steps whicb i want to repeate as i run the jmeter.
the script runs fine but my problem is that when it runs the steps (one of the stpes include creating a user),i want it to create different user and store in the database,this is possible using the "user parameter" ,but it does not work when i give it a file name to pick the different values while executing the each step recorded.
whereas the script does pick the values specifed in the user parameter when given right away instead of giving it a file name to pick up the values from.

PLease help me with this problem,it is urgent,

Thanx in advance to you greate people out there,
VS