IDE Path variables, how to use...

Hi,

I have defined a Path variable in Settings->IDE->Path variables like this: project.dir = c:\projects\myproject

Then i want to use that variable in the Settings->IDE->Resources and define a URI location like this: project.dir\WEB-INF\tld\my.tld..

I can't find any doc how to use those path variables, how do i address them?!

Thanks i advance, Frank