Check these links for a possible solution.
Wikipedia page of editing software
Audiobook Cutter (3 versions)
If you have the patience "Audacity" will do it for you but not automatically.
You will need to download LAME to export mp3 files from Audacity.
(Go to the Audacity web page and go to the page for your operating system. )
Looking for what type of software can accomplish this...medium technical ability. MAC or PC.