Format a cell to display week number starting from a certain date

I'm trying to format column B to display the week number (1-4) starting from a certain date and cycle to the next week every Monday using the date provided in column A. For example:

If I start at July 11, 2011 (Monday) in column A, I want that to display "Week 1" in column B. I want this to happen for all dates up until July 18, 2011 (the following Monday), when column B should display "Week 2". I want this cycle to continue, but after it reaches "Week 4" I want it to start over and go back to "Week 1".

Is there any way to do this? I would enter the week number manually, but unfortunately I have over 30,000 rows of data. Any help is greatly appreciated!

This is what I had previously, but it just returns the week number out of the year. So July 11, 2011 returns "27". I want the numbers to cycle from 1 to 4 like I described in the post.

Nevermind, I solved the issue:

=IF(MOD(WEEKNUM(date-(startdate),1),4)>0,MOD(WEEKNUM(date-(startdate),1),4),4)