Gearbox stop leak.

My current skip/runabout is a seat Ibiza and has developed a gearbox oil leak. It appears to be coming from a joint not from the output seal. as the car is worth nothing I dont fancy taking the gearbox apart to replace a gasket so am looking for an easy solution. Anyone had any sucess with "gearbox stop leak" or is only sucessful on a leak from a seal ? . (as opposed to a gasket)