CATT

I am creating a CATT program which has cost center group as a variable. Our cost centers are at plant level and some plants have 3 cost centers and some have 12. How is it possible to create a CATT program where the number of cost centers won't matter? For example when I create one with 12 cost centers then when uploading for 3 cost centers it gives an error because it thinks that it needs to populate 12 cost centers.....any help would be appreciated....