I'm just having no luck trying to get this calculation to work... and
I'm sure it'll probably be fairly basic.

Basically I'm trying to count the number of working days someone has
been off work sick. (Monday to Friday and not counting Saturday or
Sunday).

I have the first day of absence in DDMMYY in one column (D3) and then
todays date in E3 (using the =NOW() function). But whenever I try to
use the Network days function, which I saw recommended on
dailydoseofexcel.com, i.e. =NETWORKDAYS(D3,E3) , I just get a #NAME?
error.
If I do Insert Name Define and put Networkdays, I get a #REF!
error.

I am using Excel 2000. Any help would be greatly appreciated!

Many thanks.