So I did my research and found out that I had to write some server-side script/module to support this. I tried Wowza Server and wrote a Java Module which defined a handler function so the AS was able to call
netconnection.call("handler_function", null, "myStream", arg1, arg2);
But sadly, I am using a third-party streaming cloud so I can't write server-side code. Is there any way to add the CuePoint only on the client side with ActionScript?