validation on screen select-options
In my selection-screen one select-option is there.i want to validate my select-option field.
i have written the query like
select single * from ekpo into ekpo where ebeln in s_ebeln.
if sy-subrc ne 0.
message e999 with 'enter the valid po'.
but in my selection screen i want to enter 2 correct values and 2 wrong values.
it has to stop while the wrong values execution.but i am not getting that.i am getting the correct 2 values.
how can i validate & what is the perfect validation procedure during the select-option?
Please help me.
Thanks in advance.