You could also try like.
PARAMETERS: RADIO1 RADIOBUTTON GROUP r1 USER-COMMAND UC, RADIO2 RADIOBUTTON GROUP r1, RADIO3 RADIOBUTTON GROUP r1. selection-screen begin of line. selection-screen comment 2(15) w_text1. SELECT-OPTIONS: SO_DATE FOR SY-DATUM. selection-screen END of line. INITIALIZATION. RADIO1 = 'X'. W_TEXT1 = 'POSTING DATE'. AT SELECTION-SCREEN ON RADIOBUTTON GROUP r1. CASE 'X'. WHEN RADIO1. W_TEXT1 = 'POSTING DATE'. WHEN RADIO2. W_TEXT1 = 'CLEARING DATE'. WHEN RADIO3. W_TEXT1 = 'OTHER DATES'. ENDCASE.
Regards,
Philip.