3cx - Dialer for mobile extensions

We are using a 3cx phone system and we have some mobile-only extensions. We are looking for a way to receive an incoming call on the mobile extensions when dialing out. Potential solutions: 1.) Use soft-client interface or specific software where you enter the number to be called. It will then establish a call to the mobile and once connected, it will dial the outside number. 2.) Have some kind of UI or API call which will establish a call to the mobile extension and then provide a dial-out tone so that the number can be dialed using DTMF. Any other way to reach the same target, incl. applications in parallel to 3cx, are equally welcome