If you want to have a block of code run, just write a script. The following script opens the video player, loads a movie and plays it:
runMCI | mci | mci := (self subpartNamed: 'Media Control Interface'). "Open the digital video device." mci send: 'open digitalvideo wait'. "Load the tahiti movie. It must be in the current directory. Or you must specify a full path name in the command." mci send: 'load digitalvideo tahiti.avi wait'. "Play the movie and don't return until the movie is done." mci send: 'play digitalvideo wait'. "Close the digital video device." mci send: 'close digitalvideo wait'.