There is a way to manipulate the volume of smaller parts of the file in SOUND FORGE Audio Cleaning Lab without actually breaking it up into multiple audio objects. However, it's not via ranges, which are just a tool for copy & paste operations etc. The tool you should be looking at is the "volume draw" mouse mode (e.g. available via the "Options" menu). This will enable you to draw an automation curve for the volume on top of your waveform.