Hi Katrice,
Try ON_DATA_CHECK. If that too doesn't fire when you want, you may want to create an event handler method for each of the ALV events and set breakpoints in them just to see when they fire and find out if any of the ALV events can be used for what you want.
Also, if you want to capture the date value right after F4 help, the view's hook method wddomodifyview may work for you if no ALV event does since it gets executed upon return from F4 help.
Cheers,
Amy