Home Depot!!!!! Basic wiring book will have the answer!

assuming all five lights are on same circuit already you need to have power from the source (circuit breaker) go to the FIRST 3way dimmer switch, then through the five lights, then to the LAST 3 way dimmer switch. That way the first and last switch control the lights...must use 3 way dimmers (obviously) and four-wire wire with the extra wire as the "common" line...you may need to rewire the entire circuit with the four-wire--check either Home Depot's DIY book OR Time's DIY book. If I check myself I will post again.

You can only use a 3-way dimmer on one side of the circuit the other switch will have to be a normal 3-way switch.