try:   
        ### look if there is an open image
        strPath = App.ActiveDocument.Name
        strFile = App.ActiveDocument.Title
        strDir = strPath.rstrip(strFile)

    except:
    ### no document open
        # MsgBox
        App.Do( Environment, 'MsgBox', {
                'Buttons': App.Constants.MsgButtons.OK,
                'Icon': App.Constants.MsgIcons.Stop,
                'Text': "You must have an open image. Script will be aborted.",
                })
        return