I have a list of numbers, some are 5 digits the others are 6 digits long.

For some of the 6 digit numbers there is a complete set, i.e. XXXXX0 through
to XXXXX9. Where this is the case I want to replace the existing 10 entries
with a single 5 digit number i.e. XXXXX. Where there is an incomplete set
of 6 digit numbers, then I want to leave the existing 6 digit numbers in the
list.

I also want all existing 5 digit numbers to be included in the finished
list.

How can I get excel to do this?

TIA.

Chris.