How do I divide a volume to smaller ones in a meshed geometry?

I have a meshed rectangular cube with following dimension 1*1*3. it includes 24000 cubic cells . I made a secondary mesh in which every 64 cells make a new cubic mesh (coarser meshes). Also I have coordination of all 24000 cell centers and some other parameters like pressure and velocity in every single cell in xls, txt and dat formats. I need to put evrey 64 cells (which are besides each others) together in a regular order and make coarser (bigger) meshes to average those data in the bigger cells. There will be 24000/64 = 375 meshes.

In other word, how can I divide a meshed volume like a cube to smaller ones so that the same numbers of cells locate in every smaller cubes, so called averaging in geometry!

Thank you,

Omid