abrad41, if you connect you scanner output up to the input of the PC's sound card, then bctools offers the following feature - "Advanced recording features to provide unattended scanning, logging and recording"
"You can also configure bcTool to automatically record all received transmissions. Options are provided to automatically stop recording (and optionall move the scanner on) after a set duration, automatically delete short recordings, define filename structure and set recording format and bitrate." See
http://www.bctool.org/index.php?s=screenshotsI've never used it, but sounds like it would do what you want.