Matching two different data sets
 

I have two seperate data sets. One showing people in drug treatment, and the
date they entered treatment. The other is an agency that refers clients to
the treatment agencies. I have unique identifiers for clients
(Initials/DOB/SEX), so have used vlookup to match them. However there can be
duplicate clients as they can be reffered more than once and the dates might
not exactly match, but would be counted as matching if they are within two
weeks either side.

(not sure if that makes sense)

Does anyone have any ideas? I'm a bit stuck.