help in selection screen

hallow

i wont to do a 2 check for the selection screen c_course but the program bring me erorr that i cant do 2 selection for c_course .

how can i do that

SELECTION-SCREEN BEGIN OF BLOCK b1 WITH FRAME TITLE text-t01.

SELECT-OPTIONS c_course FOR pchdy-objid_str NO INTERVALS OBLIGATORY.

SELECTION-SCREEN END OF BLOCK b1.

AT SELECTION-SCREEN ON <b>c_course.</b>

*================================

IF c_course[] IS NOT INITIAL.

SELECT SINGLE istat_e

FROM yhr_score_page

INTO check_course-istat_e

WHERE objid_e IN c_course

AND istat_e = '1'.

IF sy-subrc NE 0.

MESSAGE e013.

ENDIF.

ENDIF.

• AT SELECTION-SCREEN ON <b>c_course.</b>

**================================

*

• IF c_course[] IS NOT INITIAL.

• SELECT SINGLE objid_e

• FROM yhr_score_page

• INTO check_course-objid_e

• WHERE objid_e IN c_course

*

• IF sy-subrc NE 0.

• MESSAGE e018.

• ENDIF.

• ENDIF.

regards