Calculate Week Number

Hi Folks

I need a formula to generate a week number for the years 1998, 1999 and 2000.

Short of manually creating a list of dates and typing in Week1, Week2 etc, is there an automatic (and hopefully quicker and more simple) way of achieving the same result?

I've checked the online help, but Excel does not appear to have a WEEK function.

Any suggestions appreciated.

JAF