Hi Avi,
u can try this also :
IF wa-kschl = 'aa' or
wa-kschl = 'bb' or
wa-kschl = 'cc' or
wa-kschl = 'dd' or
wa-kschl = 'ee' or
wa-kschl = 'ff' or
wa-kschl = 'gg' or
wa-kschl = 'hh' or
wa-kschl = 'ii' or
wa-kschl = 'jj' or
wa-kschl = 'kk'.
Endif.
But better I will suggest use ABAP help by pressig F1 key on key words to get the details of syntax.
BR,
Prakash