But he wants power from the VGA signal, which you can't get. Amplifying the signal with a transistor will work, IF you have an external power source, you're not going to be able to get more than a minuscule at best amount of power from a VGA 'signal' lines. It would be workable with a transformer, latching relays and a large capacitor buffer, for very low duty cycle infrequent pulses. But that's a LOT of circuit to build to avoid having to run a separate power line or put a battery in.