How to get my ex to admit he misses me?

What can I do to talk to him? I need to talk to him very badly but I can’t get hold of him. We wotk together before now he move to another place. He calls to my job but he does’nt look for me. He always look for out friend and ask “how’s everyone?”. But never ask me and want to talk to me. I don’t know why he still calls at my work when he does’nt have any close friend here except me? Is he trying to find out What I’m doing and just try to mention my name. How can I get him that it will not come out that I’m running after him or harrassing him. I don’t want to be told I’m harrassing man. I still want him to be my friend. I hate having a miss understanding to your ex. We both are married had affair but can we reamain as friend even he got caught with his wife? I still want him though even just talking to him to the phone and not seeing personally. It really did help to relieve my stress specially the kind of work we do. It’s nice to fell that your able to express your frustration in everyday life to a friend. Please help me to make a plan.