Peo Sjoblom wrote:
WEEKNUM is part of the Analysis ToolPak, toolsoptionsadd-ins and if it is
selected clear it, close and restart Excel and select it. If it is not
selected just select it


It just happened again. ATP was selected, so I deselected then
reselected it and all is good for now. I have used this formula in
worksheets for several years, why all of sudden is it getting stubborn?

By the way: Excel 2000 SP-3

Thanks for the help,
GeoK