Specify order in which coordinates of atoms in subunits are exported?

Hi all,

Suppose I have a molecule and the atoms in this molecule have been grouped together as a subunit. I then proceed to replicate this molecule in a unit cell box such that

   --------------------------------------

   |    subunit1  subunit2      |

   |                                     |

   |    subunit3  subunit4      |

   |                                     |

   |    subunit5  subunit6      |

   |                                     |

   --------------------------------------

Is there any way to get Materials Studio to export all the coordinates of the atoms in subunit1 followed by subunit2 and then subunit3 and etc in a .pdb file? Currently it seems like the way Materials Studio is exporting the coordinates of the subunits can be a bit haphazard - for instance, subunit3, subunit4, subunit5, subunit6....?

Thanks!