Describe what you want to do. Always trim the end silence to a specific length? Truncate Silence can do that. For example, if you want the silence at the end to be truncated to 500 milliseconds (ms), set both Min and Max to 500 ms. Setting Min and Max to the same amount means you can ignore the compression factor.
As long as there are no silences elsewhere in the selection of 500 ms or greater, the end silence only will be truncated to 500 ms.
If you are not getting the silence truncated right down to 500 ms, increase the threshold (make it a less negative number).
See: Audacity Manual .
You could also look at this plug-in: Trim Silence which truncates silence at the start and end only to almost nothing, but never truncates silence elsewhere in the audio. It may be easier to use (if you do not select the start of the track) if there are near-silences in the audio of the track that are meant to be there.
Gale