If I understand correctly then you want the difference between 2 dates
including the start and end date i.e. 1/1/2007 - 30/9/2007 would return 9. If
my understanding is correct then this will do it.

=(YEAR(B1)-YEAR(C1))*12+MONTH(B1)-MONTH(C1)+1

Note you will have to change the cell format to General after entering this.

Mike

"Eric" wrote:

Does anyone know how to determine the number of month between 2 periods? such
as
23 Feb, 2006 and 1 Apr, 2006, it returns 2 months difference and not
counting the starting day. And always start to count Feb, 2006 and Apr, 2006.
Does anyone have any suggestion?
Thank you in advance
Eric