SolidWorks 2012 changed how you create linked values. The new process takes a little longer than the old way. The benefit to the new way is that what is linked is clearer to different users because it is in global variables. You will see in the following video that I set the value as a variable, then link dimensions to that variable. They say a picture is worth one thousand words, so I hope a video is worth one million.
EDITOR’S NOTE: SW has restored the Linked Values tool from the right-click shortcut menu as of SP1 so the method demonstrated in this video is only necessary if you’re using SW2012 SP0.