Not updating formula after data refresh

[Peter Davison]

Hi.
I have the following formula in cell L5 onwards to remove the last 2 characters of the full Post Code in Cell N5 onwards
=left(N5,LEN(N5)-2))

Column N is being updated from a separate work book, but after the workbook has updated I notice that the formula above does not update and displays the the full post code in column L that is shown in column N.
If I retype the formula and copy it down to all cells it will work.
Any ideas why this formula won't update automatically?

Any help would be good thanks.

 

[Peter Davison]

Ignore the above I have just realised what is wrong, there was training spaces at the end of the post code.
Apologies