Here is a method to link a note on a part drawing to its quantity used in an assembly. It works for parts whose quantity can be somehow entered or calculated in an equation in the assembly. The simplest example would be a linear pattern of components, such that you can enter the pattern quantity directly into an equation.
1. Create a sketch in the assembly consisting of one construction line with a length dimension.
2. Make an equation such that [line dimension]=[component qty]*1. You have to go through an equation rather than link values because you can't link values on two different dim types.
3. Create an in-context sketch on the part, also consisting of one construction line. Make the endpoints coincident with the endpoints of the assembly sketch.
4. On the part drawing, show the sketch, add a ref dim for the line length, and create your note with a link to that ref dim. You can then hide the sketch and the ref dim created.
