hi Heinz,
The lookup procedure can be a form, so I'd likely try this by setting the (regular) lookup button to call the form and then do what you want on the form. That said;
>> But this is not the problem, the question is, is it possible to create manually a button which calls a browse in selection mode and fill a string field of the form after coming back with a selected record.
there's a lot to unpack here.
creating the button manually - that's obviously simple enough.
calls a browse in selection mode - also easy enough
"coming back with a selected record" - that's a lot more tricky, because remember in the web you "never come back", you just go forward.
So the approach here will be very different depending on if the lookup is a popup or a page. that would be my next question.
but, I'd go back to the beginning, I think a regular lookup will do what you want, with a LOT less effort...
cheers
Bruce