I am assembling a large number of tiles that have spacing between them.  The spacing is a repetitive dimension always the same but I want to be able to change this dimension once it is all assembled.  Using a global variable works but it is tedious.  Am I doing it wrong?  When creating the dimension it won't let me type "=" and show the global variables.  I need to create the dimension constraint, find the constraint I just created in my tree, edit it, then I am able to type "=" and it will show my list of global variables.  This is very tedious.  Is there an easier way?