I have up to about 5000 rows of data on a sheet, it is made up of original
and updated information about customers.

Column A is an ID number. What I want to do, by code, is to delete the
single entry customers (those who have no updated information).

I have sorted by column A to bring both original and updated together but am
now stuck.

I have tried inserting a column (A) and putting the following in to identify
the ones I want to keep but cannot figure out how to delete the remainder:

=IF(COUNTIF($B:$B,B2)1,2,1)

Thanks in advance.

Gareth