1. A system for implementing an asynchronous access passing mechanism between a client and an external function, comprising: a client operative to couple an access mechanism object with a user-interface object in an application program, and operative to pass to an external function a reference to the access mechanism object; the client being operative to communicate events associated with the user-interface object to the access mechanism object, and operative to change a value of the user-interface object upon request from the access mechanism object; the external function being operative to determine a first user-interface object value via the access mechanism object and being operative to indicate to the access mechanism object a second user-interface object value; and the client being operative to determine the second user-interface object value from the access mechanism object and to reflect the second user-interface object value in the user-interface object coupled to the access mechanism object.