Refresh Sheet With Shift+F9

Hi all, I am a Jet noobie, so this might be a simple question.

In Excel 2007,

If I have a sum
=nl("rows","item","description","no.","1206")

To get this to work in some Workbooks I have to press the 'Refresh' button (from the Jet ribbon). In other workbooks I can just enter the formula and it will work, or can just press Shift+F9 to recalculate the sheet and it will work.

It seems to be workbook specific?? But if I then send the workbook to a colleague they can just Shift+f9 and it will calcuate.

Has anyone come across this before? Basically, I want to be able to only calculate the current sheet (not the workbook), so do not want to use the Refresh button on the Jet ribbon (which does the full workbook). It just annoys and confuses me that it works for some workbooks but not for others.

Any help would be much appreciated.