Functions across .as files or in timeline?

Is there a way to call a function from another .AS file within your classpath? Better yet, is there a way to call a function from your timeline of a .fla to a .as file in your classpath? Here is the error I am getting:

ReferenceError: Error #1065: Variable currTool is not defined.
 at Cir/onMouseDown()

currTool is a function on frame 1 of my main timeline and Cir is one of my .as files.