doubt in assigning

Hi,

i want to compare the value of bkpf-xreversal with 2 and if it is having a value contains 2 then in the output the amount value should be shown in negative for which i had written code as below

IF BKPF-XREVERSAL = '2'

AND BSEG-BELNR = BKPF-BELNR.

BSEG-WRBTR = -(BSEG-WRBTR)

ENDIF.

but it was showing some syntax error now i want to know if i have to assign negative value what is the procedure

i have tried like this also

IF BKPF-XREVERSAL = '2'

AND BSEG-BELNR = BKPF-BELNR.

BSEG-WRBTR = 0-BSEG-WRBTR

ENDIF.

plzz suggest me any solution