Detatched Garage wiring

[Redline]

I have a detached garage, and the previous owners buried 2-wire in conduit from a dedicated 20A circuit to the garage. Now there is constant power out to the garage for the garage door opener, a shoplight and a few outlets. My question is, would there be a way without digging up the conduit and changing to 3-wire to have a 3way switch in the house and in the garage, as well as have constant power? Id like to be able to turn the lights on from the house, and then turn them off from the garage, or vice versa, but still keep constant power for the garage door...

Thanks in advance.

[Snoonyb]

What is the conduit material?
What is the size of the conduit?

[HayZee518]

Merely swapping out the two wire with a three wire wouldn't solve your problem. The three wire gets its supply at the house and two travelers go to the garage.
The neutral is carried out to the garage via the white wire. The load ends up being the odd screw on the switch. You need the two wire to have a source of continuous hot to the dedicated circuits in the garage. A better means would be to use a four wire if you can find it.