Clear parameter after execution

Hi Experts,

How can I clear my selection screen after execution(f8)?

I cannot put my clear code at  AT-SELECTION-OUTPUT because when I press enter it also clear my parameters.

My requirement is to clear my screen after ececution(f8).

I've tried to put my clear code at START-OF-SELECTION Clear: p_tire, p_sup, p_head. and nothing happens.

Thank you.