Restart F8 function in 'AT SELECTION-SCREEN'

Hello Experts,

I am developing a report with a selection screen:

on 'AT SELECTION-SCREEN', validation is performed and error message(' E ') is shown if no record is retrieved based on selection:

Question:

After i input data in the selection screen ( force input not to retrieved record ), i pressed F8 ( execute ). the error message is shown.

i corrected that data and just press 'ENTER' key. No error message was shown since a record was retrieved.. but the problem is, it now continues execution on 'START-OF-SELECTION'.

My needs is only the F8 ( execute ) key should be able to execute 'START-OF-SELECTION'.

is there a way i can 'REFRESH'  the F8 whenever an Error is encountered in 'AT SELECTION-SCREEN'?

thanks a lot!

Carl