I think that the best thing to do will be to buy separate tickets. I don´t think that you can break up a trip like that, leaving a couple of days between the two legs. I have been checking in http://voyages.sncf.com , and I have seen that to travel from Dijon to Troyes you will have to change either at Laroche Migennes (and get a bus) or at Culmont or Chaumont (and get a Corail train). The price for a trip on the 26th of October will be only 25 Euros pp, not too bad.

Kind regards, and hope everybody is OK down in Montevideo Covadonga Bilbao - Spain