On your 13th (inserted) worksheet (Master - which should be the First
Worksheet (that is furtherest to the left)) in cell J40 enter:
Sheet1:Sheet12!J40 (rename Sheet1 and Sheet12 as appropriate)
That should do it..

"M@ Brereton" wrote in message
om...
I am trying to add numbers from multiple spredsheets in one file.

The file is a timetable file with twelve spredsheets. One for each
Month. I am trying to add Cell J40 from 12 spreadsheets as they are
entered