Try this

=(A1-DATE(YEAR(A1-WEEKDAY(A1-1)+4),1,3)+WEEKDAY(DATE(YEAR(A1-WEEKDAY(A1-1)+4),1,3))+5)/7

Mike

"Seanie" wrote:

How could I return the week number that equates to a particular date?

I have tried =weekno(a1), but firstly my weeks begin on a Monday, not
Sunday and secondly I want to express a fraction of a week also

For example
10/11/08 = 46.00
11/11/08 = 46.14
12/11/08 = 46.29 etc etc
17/11/08 = 47.00
18/11/08 = 47.14 etc etc