just clicked value DOUBLE SELECT on FORM

I have a FORM with a double select on it.

How do i get the value of the item in the list i just clicked in the left column to add? And how do i get the value when clicking an item in the right column to remove it?

I always recieve the final result of the double select! I just want to get the value i just clicked.

tried ajax events?

that’s the way i tried everything. But no success. There must be a way to only get the ‘just-clicked’ list-item!

It seems very unlikely that it 's not possible to get the clicked value. Nobody ever needed this?