Good Question....Tania.
by running Ad-hoc query? may be, thousand ways to do stuff in SAP but like I always give this example, no matter how much money spend by Airbus they could not make planes pilot-less we still need end users to at least populate certain fields/masterdata, I bow down to take your suggested way over my proposed solution.
by the way there would be no need of C column in Z table if ABAPer can code it correctly within the function to bring along number of active employees with medical subscription (very simple I presume) .....here we go thousand ways doing stuff with SAP
KR
Sid