I guess I just have to ask... WHY? What is the point of this exercise? In FAA-land it is unknown, even before GPS became universal (for example, when I learned to fly in 2001). There used to be a magnificent piece of avionics called the KNS80 which could do this kind of thing. I even tried to read the manual (my plane had one before the previous owner installed a GNS430, so it came with the manual). Programing it in the air, in response to something like "direct DOCAL", would be challenging, to say the least.
Do ATC in the UK really give this kind of instruction to VOR/DME equipped (no GPS) aircraft?