check money in the trunk Freepbx

I need to check if my trunk output have credit to make calls. I need every x minutes / hours (programmable) the system can make phone calls to external phone numbers (programmable) with the trunk (programmable) and understand that if the call takes place on a regular basis, or credit is exhausted. In the event that the credit is exhausted immediately send email alert (programmable text and e-mail address specifying which trunk is empty). The system must make calls without playing the internal telephones. The system does not let me spend money in the call, so it must identify whether the trunk have money using number recognition caller via the trunk. If we receive the phone call of course it means that the other trunk has the money to call.