CodeBlock macro should support file references as read-only code

It would be very convenient if the CodeBlock macro would allow you to provide a file reference via URI, ideally with starting and ending line numbers. Obviously this would need to be read-only since you won't in general have any way to update the referenced file, but even read-only access would be VERY useful in building architectural wikis. 

Some clarification: 

The problem I am trying to avoid that when changes are made to the file that the code in the wiki was extracted from - those changes are not reflected in the wiki. What I want is for the CodeBlock to retrieve the lines in question from the current file and display them in on the page.  This should not pose any significant security concerns because you are only displaying source code (not executing it) and it can be escaped as needed to ensure it is clean.