With your data in A1:A1500, in cell B1 put the following formula and copy down:-

=IF(COUNTIF($A$1:$A$1500,A1)1,"Keep Me","")

Now select all the data and sort on Col B in descending order.

Then just delete all the unwanted records at the bottom.

--
Regards
Ken....................... Microsoft MVP - Excel
Sys Spec - Win XP Pro / XL2K & XLXP

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"Gareth" wrote in message
...
I have a sheet of data which is made up of all customer details and updated
ones (all is approx 1,500 and updated 25).

Each customer has an unique ID number so I am able to sort the data so as to
get the 'old' and 'new' data next to each other.

What I want to now is delete every row apart from the customers who have
updated details.

So I would be left with 50 records.

Thanks in advance.

Gareth