Hi Alberto,
The correct place to do stuff like that is in the form you are returning to.
There's a specific "after lookup" embed point for that.
At that point you have the unique record identifier - if you need more from the record then you need to open the file, fetch the record, and copy whatever you like to the session queue. (Incidentally the template has options for this, Lookup Settings, More Assignments).
Remember that even if the did it in the browse, when the select button is clicked, you'd still have to fetch the record. All you get from the click is the row id.
Cheers
Bruce