Help Not Exists

[#1]

I need help to do the following expression does not exist:

set @DataMesAnt = CAST(CONVERT(CHAR(10), GETDATE(), 121) AS SMALLDATETIME)


IF NOT EXISTS(SELECT * FROM NfiCabV ncv JOIN NfiItmV niv
              ON  (
                     ncv.Nfi_Planta = niv.Nfi_Planta
                     AND ncv.Nfi_NotFis = niv.Nfi_NotFis
                     AND ncv.Nfi_Serie = niv.Nfi_Serie
                 )
 WHERE  ncv.Nfi_Planta in ('01','06')
        AND ncv.Nfi_DatEmi = @DataMesAnt
        AND ncv.Nfi_OriNfi = 'P'
        AND ncv.Nfi_SitNfi IS NULL
        AND ncv.Nfi_Serie IN ('U1', '1') )

BEGIN
 set @DataMesAnt = CAST(CONVERT(CHAR(10), GETDATE()-1, 121) AS SMALLDATETIME) 
END 

can anyone help me?