  The influence of La non magnetic impurities on the spin dynamics of
CeCoIn$_{5}$ was studied by inelastic neutron scattering. In La-substituted
systems, the spin resonance peak (observed at $\Omega_{res}=0.55 meV$ in the
pure system) is shifted to lower energies but the ratio
$\Omega_{res}/k_{B}T_{c}$ remains unchanged. The excitation broadens till it
reaches 0.3 meV equal to the value of the quasi-elastic signal in the normal
state. The evolution of La substitution is compared with the evolution of the
magnetic resonance in Ni and Zn substituted YBa$_{2}$Cu$_{3}$O$_{7}$.
