I understood what were you suggesting, but in that way it would be better to distribute all package, cause after changing my objects without real callback other reactions will be useless.
And if I provide a real callback function in a drawing, it would be rather difficult to make changes in it when it is already embedded in a drawing.
I could take it if there was nothing to install at user PC, but if there's no way to do it, it would be better to produce the program itself, IMHO.