If this is in access then I would code two make table queries using whatever split criteria you are needing. Then you may want to write a find duplicates query between the two new tables to make sure that they are unique.

If you are using excel use VBA to check the data on your source sheet according to your criteria, then copy the data from your source sheet to whichever destination sheet is indicated by your criteria.

With a litte more detail I could create some sample code for this point.