How do you determine the right Class ID number?

// Similar to getActiveXInstalled but checks also if the activex has to be updated
this.getActiveXInstalledToUpdate=function(){
    if (this.activeXProgId){
        try{
             var a=new ActiveXObject(this.activeXProgId);

             // A version is installed, but is it the current one?
             var installedVersionArray = a.Version.split(',');
             var currentVersionArray = this.activeXControlVersion.split(',');

             for (var i = 0; i < 4; i++)
             {
                  if (parseInt(installedVersionArray[i]) < parseInt(currentVersionArray[i]))
                 {
                     // installed version is older then the current one
                     return true;
                 }
             }
        }
        catch(e){
        }
    }    
// no update required
return false;
}