Dante and Vince

This is Dante the Russian kitten and his feline companion Vince.
Dante has been in his new home almost two weeks. He is a very clever kitten, in fact, a little too clever.
Vince enjoys the freedom of a garden and outside play. Vince access' the outdoors using a microchip specific cat flap.
Yesterday Dante unexpectedly followed Vince outside. Everyone, including me thought that as the cat flap was only programmed for Vince it would not allow Dante the kitten outside. How wrong we all were. The microchip cat flap lets ANY cat outside but only Vince back in!! Dante was found safe and sound but that leaves the dilemma of how to allow Vince the older cat his freedom without allowing kitten Dante outside. I wonder how many people this has happened too and if there is a cat flap on the market that also controls who goes out as well as who comes in.