drop down list showing dates instead of numbers

[Guest]

I have 2 workbooks. Workbook 1 contains named ranges one of which is a list
of payroll numbers. Workbook 2 has a column to select these payroll numbers
in a drop down lists using validation, lists, the named range. This has all
worked perfectly well for a couple of months, however, today the drop down
list no longer displays the payroll numbers as numbers but as dates. When one
of the dates is selected it drops the number into the cell in the correct
format ie payroll number. Does anyone know why this is happening?

 

[Guest]

Check cell has not been formatted as date

 

[Guest]

Thanks for replying. The cells in workbook1 are set to a custom number and
the cells in workbook 2 are set at general. Since posting my enquiry I've
changed the format on workbook 1 to number and this allows the workbook 2 to
work correctly. However there are approximately 70 workbook 1s all set up in
the same way ie custom numbers and they are having no problems. This
particular workbook only started having problems today and has been in use
since the beginning of July.