Send dtmf from IVR

I have a phone system at the front door of office my building and run by my landlord, and phone at the door calls one of my office phones and to let someone I press 9. What I am looking to set up an IVR that has a hidden code where it will return a 9 DTMF tone to the person it they type in the correct code.

Does anyone know how to set up a custom destination or something similar to have the Asterisk server send a 9. I was able to find the sendDTMF command ( but I am not sure how to set that up.