Rodrigo,
This a function I wrote for Clipper (DOS) you can reuse in Fox.

function valicuil
parameters mcuil

if substr(mcuil,1,2)=" "
sound(warn)
Msg("NRO. DE CUIL VACIO")
RETURN .F.
endif substr(mcuil,1,2)=" "

cuila=0
cuila=cuila+val(substr(mcuil,1,1))*5
cuila=cuila+val(substr(mcuil,2,1))*4
cuila=cuila+val(substr(mcuil,4,1))*3
cuila=cuila+val(substr(mcuil,5,1))*2
cuila=cuila+val(substr(mcuil,6,1))*7
cuila=cuila+val(substr(mcuil,7,1))*6
cuila=cuila+val(substr(mcuil,8,1))*5
cuila=cuila+val(substr(mcuil,9,1))*4
cuila=cuila+val(substr(mcuil,10,1))*3
cuila=cuila+val(substr(mcuil,11,1))*2
csuma=cuila/11
entero=int(csuma)
resto=cuila-(entero*11)
if resto=0
mdigi=0
else
mdigi=11-resto
endif
if val(substr(mcuil,13,1))<>mdigi
sound(warn)
Msg("NRO. DE CUIL ERRONEO")
RETURN .F.
ENDif val(substr(mcuil,13,1))<>mdigi

RETURN .T.

HTH.



>Hi
>
>Somebody has a procedure to check valid cuit/cuil?
>
>TIA