Does anyone know how to do this?

[Chris230291]

Hello. What i want is a circuit that can monitor the voltage on the "+" pin of a 3 pin fan header on a computer motherboard. Then "copy" that voltage and replicate it from an external power source (PC power supply), but with enough current to run anywhere up to 8 fans (for example). My plan is to have one fan connected directly and it's speed controlled by the computer. The circuit will monitor the "+" output and replicate it for other fans, allowing me to run multiple fans at the same speed as the one directly connect fan. I hope that makes sense?

I know nothing about designing electronics, but if someone has a solution i am more than capable of assembling it.

Thanks,
Chris