An execution engine embeddable in a plurality of host application programs to control execution of code in each of the host application programs is disclosed. The execution unit includes a command unit, an execution unit and a host call unit. The command unit receives commands from a host application program in which the execution engine is embedded, including a command to execute a sequence of platform-independent instructions. The execution unit executes the sequence of platform-independent instructions until an instruction indicating either a break event or a remote procedure call is detected. The host call unit initiates execution of one or more procedures in the host application program in response to the execution unit detecting the instruction indicating a break event or a remote procedure call.