You can also enter the date of the first day of your fiscal year into a global date field and use regular calcualtion fields without a custom function to compute these. You may find that you can adapt the above calcualtions to such a use--an option to consider if you don't have advanced.
Thanks for the replies. i'll give those a try. :)
Follow up: I've seen those custom functions before during my online search. I noticed that it will only take a Day (StartDay) and a Month (StartMonth) and compare those with the "TheDate" that I have. Problem is, I'll have discrepancies when the calendar year crosses over.
In my example, 25 September (2011) shows as "Week 1" but it also shows 29 September (2012) as "Week 1" which is true given that they're on the same calendar year.
Is there a way to incorporate a "StartYear" as well within the custom function so that it will be more accurate?