Copy signal bindings

[LCID Fire <lcid-fire gmx net>]

I'm currently trying to modify the GtkWindow to send all key strokes not
being handled by any Widget to a specific widget in my app.
AFAIR the way to do this is to get the specific widgets' binding set via:

gtk_binding_set_by_class(GTK_WIDGET_GET_CLASS(source))

and then add all the signal entries present in the source to the window via:

gtk_binding_entry_add_signal
(
 destinationSet,
 sourceEntry->keyval,
 sourceEntry->modifiers,
 currentSignal->signal_name,
 currentSignal->n_args,
 ...
);

The problem I get with this is that gtk_binding_entry_add_signal wants a
vararg - and AFAIK there is no way to build a vararg from GtkBindingArg,
is there?
Could somebody give me a hint how to do this properly?