gironzolando ho trovato questo:

codice:
 
// Create new instance of LoadVars() object... 
fileExists = new LoadVars(); 
// Not a clue what this is...  :( 
fileExits._parent = this; 
// Define an onLoad handler for the fileExists instance... 
fileExists.onLoad = function(success) 
{ 
    //success is true if the file exists, false if it doesnt 
    if (success) 
    { 
        // This if block is for the case when file exists... 
        // Create a new empty movieclip that will hold the 
        // external file that is to be loaded... 
        var nm = this._parent.createEmptyMovieClip("swfHolder", 1); 
        // Load the external file into that place holder... 
        nm.loadMovie("myfile.swf"); 
        trace("File Exists!!!"); 
    } 
    else 
    { 
       // This else block is for the case when file does not exist... 
        trace("Where Is Your File???"); 
    } 
}; 
// initiate the test 
fileExists.load("myfile.swf");
E' per controllare l'esistenza di un filmato flash...
ma dov'è il controllo?
dice: //success is true if the file exists
ma qual è il nome del file?
scusate ma sono un po' un in queste cose...