Ron:
Short version, yes, there are tracing dyes made for use with engine
oil. A web sight that talks about it is:
http://autorepair.about.com/library/...aa050804b.htm.
One of the problems with an under engine leak is the varied air currents that are running around down there. It makes it hard to trace the leak because the
oil is blown all over the place. A leak from the timing case cover will end up with traces on the starter type of thing.
A pain in the butt and time consuming but about the only sure way to trace it is to completely clean the bottom of the engine and undercarriage and then put the car up on stands or a lift. Run the car and then shut it off and wait for the leak to reappear. Clean paper under the car will help show up the leak if it drips from the source, just look above the spot.
DonC