Onsite this past week a client asked if there was any way to delete a style that was being USED in the drawing.
I answered; sure if you can find it. Next time I will ask what version are you running?
NEW CIVIL 2012 FEATURE
Finding Where Styles Are Used in a Drawing
1. Simple right click the style in use and select Find Reference
(marked by a yellow triangle ).
2. Double-click an item in the dialog box to navigate to the reference in Toolspace.Typically works well, but some user input may be required. (see attached)
Had to right click View Frame Group and edit feature settings.
**NOTE:The right click menu also offers a REPLACE option.
Also checkout importing and purging styles. Download Civil 3D 2012 and New Feature Videos