On a second reading... it seems like you want to use the built-in COPIES attribute.
So if the LenZ of the Component is at or below a certain value (min height of a course), then the number of copies of the coarse is 0.
Otherwise, the value of COPIES is equal to (something like) the LenZ of the component divided by the height of a single coarse.
Found this model on the 3d Warehouse:
http://sketchup.google.com/3dwarehouse/details?mid=8a97a7ff65d55ffc8095ba2080357053