Block input and output ports have a single callback parameter, ConnectionCallback. This parameter allows you to set callbacks on ports that are triggered every time the connectivity of these ports changes. Examples of connectivity changes include adding a connection from the port to a block, deleting a block connected to the port, and deleting, disconnecting, or connecting branches or lines to the port.
Use get_param to get the port handle of a port and set_param to set the callback on the port. The callback code must have one input argument that represents the port handle. The input argument is not included in the call to set_param.
For example, suppose the currently selected block has a single input port. The following code sets foo as the connection callback on the input port:
phs = get_param(gcb, 'PortHandles'); set_param(phs.Inport, 'ConnectionCallback', 'foo');
where, foo is defined as: