de-duping a file

[scooter6 at gmail.com]

I have a rather large file that may or maynot have multiple records based
on our 'Account Number'  - there is also a 'date' field in this file

I'm trying to de-dup the file - that is, if there are more than 1 record
for 'each' account number, it should only keep the most current record.
If there is only one record for said 'Account Number' it should keep it and
do nothing - if there are multiple (2 or more) records for 'Account Number'
it should keep the most current dated one

i.e.
Account Number is   1234-5678
There are 3 records in file with '1234-5678' as 'Account Number'
One dated 01/12/13
One dated 02/01/13
One dated 03/18/13

I want it to delete both records dated 01/12/13 & 02/01/13 but keep the one
from 03/18/13

Not quite sure how to go about doing this quickly....

thanks

Scott
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