Difficult to answer, because the occupancy is what it is.
Imagine a motorway. You have a formula that works out how congested it becomes. You can make the motorway more congested by adding more cars (more calls to your centre) or closing a lane (reducing the number of agents).
You can estimate the occupancy using the CCXLAllBusy() function (see above) but occupancy will always be a result rather than an input.