How to customise the 'search a record' searches

Hi,

I am using Microsoft Dynamics CRM 4.0

I would like to add an additional searchable field to the quick find 'search a record' section.

I added the field i would like to be able to search within the Advanced Find View, however when i try to search on this field e.g Invoice number, the search does not pic any records even though the invoice number I am searching does exist and is on an active case.  

Is there anything else i would need to do in order to get this working as I have only added the field column to the advanced find view and not done any additional linking

Any help with this will really be appreciated.

Thank you