Combintion level in demantra

We are using demantra 7.3,Client want us to create a Combination level and the combination series ..They want to have drop down value in the series and Select and save more than one value for an item location combination..Like select Item A Customer B in the worksheet select the Region A in the drop down menu and save it..They also want to assign Region B to the same item and location combination..If it even possible when we use combination levels and the drop down series?

Please Help me if it is possible.