vCAC 5.2 - Can I run a vCO script before the "BuildingMachine" stub?

I am working with vCAC 5.2, and I wanted to know if it was possible to run a vCO (or other) script before the BuildingMachine stub and without the vCAC designer. I need to call a script to make a decision on which resources vCD should use, but at the BuildingMachine stub, the vApp clone process has already started.