How do I compute double integrals in Simulink?

function Fx = ExFx_fun(x,y)

coder.extrinsic("integral2")

Fx_fun=@(x,y) x^2+y^2;

Fx=integral2(Fx_fun,0,x,0,y);

end

.....................................

function Fx = Fx_fcn(x,y)

Fx=ExFx_fun(x,y);