sending additional attributes

I have been asked to modify our existing radius deployment by adding an attribute that would be sent back to the NAS clients in order to improve traffic reporting. We want to be able to Change Interim-Update settings to 1 minutes. My Question is where would that be done? Does that mean simply changing this section:

raddb/attrs # #strictrealm # Reply-Message =* ANY, # Session-Timeout <= 86400, # Idle-Timeout <= 600, # Acct-Interim-Interval >= 300, # Acct-Interim-Interval <= 3600

Or is it more complex requiring an additional column for radreply? Thank you, Ryan