Shaped laser pulses obtained by learning control can substantially influence charge transfer which has a fundamental importance in the elementary processes of physics, chemistry and biology. Using a slow collision of sodium cation and iodine anion as an example, we perform learning control simulations by solving the time-dependent Schrödinger equation based on a two-state diabatic representation. In our control scheme, the target state is updated according to the renormalized fragmentary yield in the exit channel throughout the learning iterations, to obtain the desired laser control field.