I'm comparing 2 lists of serial numbers. The first list is smaller. The 2nd
list is more extensive and contains information in 3 more columns that needs
to be added to the 1st list.

Example:

12345678 X 12345677
12345678 Mr Joe Bloggs Feb 08 £1500
12345679 X 12345679 Mr Fred Smith Apr 08 £600
12345681 X 12345680
12345682 X 12345681 Mrs Jane Doe Apr 08 £750

If the number exists in both columns, I need the remaining info (name, date,
amount etc) to be inserted at X.

Please can someone help?