How do you control the midi clock of an external program from max?

okay, i'm sure this must be covered elsewhere, but i can't find it in the tutorials or by searching the forum here:

I want to control the transport of a external device or program via MIDI, from within max. Specifically, I am trying to control the transport of two instances of Renoise from within Max, by sending MIDI data from MIDI Yoke in Max to each these programmes indepedantly or in sync. I can get both instances of Renoise to receive midi info from max, so its just how to get send midi timing information to control the transport which i'm stuck with.

Now, this is possible with one instance of Renoise via Rewire. However, it would appear that it is not possible to currently slave two instances or Renoise to max msp as Rewire master. Therefore I wish to do the same thing with one or both instances of renoise with MIDI clock and sync information which is sent from a patch in max.

I've looked at the sync~ object but I can't understand how you send timing info to Renoise with this. Presumably this is possible though? I mean the concept should be the same as if I wanted to sync an external synth or drum machine via a clock controlled in max? How would you do that?

Can anyone offer some pointers or perhaps an example patch of how I go about this? Initially I don't need to do anything that complex, just stopping and starting the transport in each programme and adjusting the speed etc. thanks in advance