I have a form which I need to submit in order to retrieve a few values according to user selections firstly, and then let he finish the filling and then submit it again.

I realize (after some soffering) that the first submition (made by a select input onchange event handler calling a js function) only works while the submit button isn't on the page ( so I hide it using server code based on a value changed after the js function runs).

My issue:

Since the js submit only works while the button isn't loaded, the user can't use the select again to shift their choice...

Already tried: (no luck for any)

Hide the input button using the hidden property.
Reload the page when the select is used.

Any clue?