How to "find" custom engines

[Gabriele Greco <gabriele greco darts it>]

I want to use a custom engine in my gtk app, the problem is that I find 
no way to tell GTK where my engine is located, the app is multiplatform 
(linux/w32) and it doesn't find the engine except if I put it in the 
default engine path (Common Files/GTK/lib/gtk-2.0/engines or 
usr/lib/gtk-2.0/engines).

I've tried both:

(in the app rc file)

module_path "my/engine/path"

(also with the absolute path it doesn't work)

and:

export GTK_PATH="my/absolute/engine/path"

In both cases gtk doesn't find my engine and starts with the default look!

Bye,
 Gabry