"Insideout designs of the mind" wrote:

I have 500 excel files all containing the same template which shows the week
by week sales of individual styles of stock. The template cotains a list of
week dates throughout the year and details of the stock.
Is there a way that I could change the dates on my template file and have
all the other files automatically update themselves from this one file.

I don't know about a template but you can refer to a single workbook with a
formula. If a date is in sheet3 of book1 then =[Book1]Sheet3!E$1 will show
the same date. You will be asked if your want to update the links when the
other file(s) is opened.

Regards
Peter Atherton