Making a local orient constraint

In my research project, at one stage I needed an orient constraint that works locally, i.e. it works only on the hierarchy below a particular transform. I believe we could do that by re-connecting orient constraint's targetMatrix. However, since I don't know how orient constraint works under the hood and it does not allow me to have dynamic offset, I had to come up with my own constraint using matrix calculations.

So I have been digging into how transforms work and how to visualize the matrix concatenation. I was successful at making such constraint. However, I am still working on adding an offset that can dynamically be changed without affecting the rotation of the controlled object. I have yet to use this on my research project (fingers crossed). But, knowing I had success with a sample hierarchy gives me hope.

Follow this thread for detailed discussion on this orient constraint. LINK

edit: (26.06.09)
Later in my research I realized that what I had found out was not the best solution for what I was doing.