Get script folder from a script tool in a toolbox

Hello,

I have some custom ArcGIS toolboxes containing script tools (v10.0 and v10.1) written in Python. Is there a way in Python to get the folder path of the script tool that is being executed? I tried but that returns the default path for the MXD in which the tool is running, which usually isn't in the same location as the script tool(s). And, the property isn't an option for my scripts.

I'm likely missing something obvious. Any help appreciated!

Lisa