initialize value

I want to display value of quantity field as blank if it contains vaue as 0.00

This is the query which i hav written.

select * from resb into corresponding fields of resb_itab_wa

where aufnr = itab_wa-aufnr AND WERKS = ITAB_WA-DWERK.

IF RESB_ITAB_WA-ENMNG = 0.

RESB_ITAB_WA-ENMNG = ' '.

ENDIF.

i.e. if the value of resb_itab_wa is 0.00 then it should display blank

So i wrote the above query. But there is no change . 0.00 is yet being displayed.

Do i hav to write something else since it is a quantity field.