Code generation failed Incorrect number of right hand side elements in dot name assignment

I´m trying to execute this function in MATLAB 2013a in a Matlab Function Block within a SIMULINK model.

function L=fcn(l0,b0,z0,F,Q,w,Emodul)
S=Emodul;
e0=8.854e-12;
er=3;
et=e0*er;
L=(b0*l0*S*z0);
end

I don´t know why but I get the following error:

"Code generation failed Incorrect number of right hand side elements in dot name assignment. Missing [] around left hand side is a likely cause. "

Could you help me?