Writing control add-ins that work on all display targets, you have to consider some limitations regarding asynchronous communication. Compared to the Microsoft Dynamics NAV Windows client control add-in extensibility framework, the Microsoft Dynamics NAV 2013 R2 framework has some limitations regarding the interface of the control add-in. The limitations come from the nature of the asynchronous communication between the clients and the Microsoft Dynamics NAV Server. All calls between the C/AL code running on the Microsoft Dynamics NAV Server and the script function running in the Web browser are asynchronous. This means that methods in the control add-in interface must be of type void and property methods should not be used.
To transfer a result from a C/AL trigger to the calling script function, just add a method to the control add-in interface that the C/AL trigger can invoke to send the result to the script.
To transfer a result from a script function to C/AL trigger, just add an event to the control add-in interface that the script function can use to invoke a C/AL trigger that receives the result.