Selecting Primary load cases

Hi,

I'm writing some OpenSTAAD code which will take load cases from an excel spreadsheet, then input them to the staad model.

So far, I've managed to create new primary load cases then add various load items to them.

however, I am wondering how do I select a primary load case, so that I can add new load items to it? Currently I create a load case, then the load items are added to it, but how can I select a pre-existing load case?