As to where you would use it - I guess that's up to you.
The part i am not so sure is how to use the SessionValueSetFromBrowser and where.
This is what i found about that call in the forum:https://www.nettalkcentral.com/forum/index.php?topic=3968.msg14860#msg14860
How do i know in the NetTalk web server with SessionValueSetFromBrowser when the values are ready to use and are set with SetSessionValue('name','value').
Or i am mistaking that function as an observer, o something smilar to a callback?