modifying the author lists field

I am having trouble modifying the abbreviated author list fields in the author lists panel. I would like to modify the vancouver style to include et al. for above three author names. 

When I attempt to rewrite the abbreviated author list to:

If ‘3’ or more authors list the first 1 author

and abbreviate with , et al. 

when I try and close the window I am asked if I would like to save the changes. If I click to save I am returned to the author lists panel. I can only close the panel if I click don’t save changes. 

Are you working with Endnote Web or Endnote? 

 --I suspect you have your Endnote preferences (edit>preferences: folder location) pointing to a write protected location or in the program folder/endnote/styles folder (which is write protected at least in Vista).  Create a folder in somewhere like “my documents” and change your preferences to point there.

I don’t think you can be working with Endnote Web, because I don’t think you can easliy edit those styles. 

Thank you for your advice it solved my problem and I am sorry I was in the incorrect forum.