jsPlumb - how to deny connection (detach) if target or source is specify?

I'm new in jsPlumb, I'm plaing with demos. I need not to allow the connection when the target or source is specify. I mean: when the target is X - connection can't be establish.

jsPlumb fires an event connection when a connection is made.

jsPlumb.bind("connection", function(info) {
    if(info.sourceId==='abc'){
      jsPlumb.detach(info.connection);
    }

});

info is an object with the following properties:

connection - the new Connection. you can register listeners on this etc.
sourceId - id of the source element in the Connection
targetId - id of the target element in the Connection
source - the source element in the Connection
target - the target element in the Connection
sourceEndpoint - the source Endpoint in the Connection
targetEndpoint - the targetEndpoint in the Connection

References :

http://www.jsplumb.org/doc/events.html#evt-connection-detached http://www.jsplumb.org/doc/removing.html http://www.jsplumb.org/apidocs/classes/jsPlumb.html#method_detach