The Studio generated the event like this:
Code:
Procedure OnGetNavigateForwardData tWebNavigateData NavigateData Handle hoToView
But it should look like this:

Code:
Procedure OnGetNavigateForwardData tWebNavigateData ByRef NavigateData Handle hoToView
Otherwise the modified NavigateData is not passed onto the next view.

It took me quite some time to figure out the ByRef was missing... I tried to add "Forward Send..." but it dit not help either.