Well, not quite. But JETDV in the video forum has come up with a script. Instructions further down thread on how to add to keyboard shortcuts, and toolbar !

Locks,(or unlocks) selected track(s). More useful than the native Event Lock tool. A handy (essential ?) tool for the toolbar, but a dedicated button per track header would be best..

http://www.sonycreativesoftware.com/forums/ShowMessage.asp?MessageID=715824

geoff