The property is meaningful only if the communication is set by the DDE as the DDE client on the "DDE" tab of this object (in the running application the communication can be disabled or repeatedly enabled by this property).
Disabling the communication by this property is not functional for change reading from the server. But it is functional for periodic reading and writing and for change writing into the server.
var oNumber = pMe.Pm("/Number0");
var bEnabled = oNumber.DdeClientEnabled; //Reading the value
oNumber.DdeClientEnabled = true; //Writing the value