The execution model of mobile code inherits from traditional remote execution model such as telnet that needs two conditions. First, the proper program must exist in advance in the remote system. Second, there should be a process in the remote system waiting for requests. Therefore mobile code also bears the same conditions in order to be executed in a remote system. But these conditions constrain an important aspect of mobile code, which is the dynamic extension of system functionality. In this paper we propose a new approach, named Function Message that enables remote execution without these two conditions. Therefore, Function Message makes it easy and natural for mobile codes to extend system functionality dynamically. This paper describes the design of Function Message and implementation on Linux. We measure the overhead of Function Message and verify its usefulness with experimental results. On the ATM network, Function Message can be about five times faster than the traditional remote execution model based on exec().