I have a 3-way switch at the top of my stairs and another at the bottom which control one stairway light.  At the bottom I have a second switch next to the 3 way switch which controls other lights in the downstairs room ("downstairs lights").  I would like to be able to turn off the downstairs lights from top of the stairs.  I would be willing to install a second switch upstairs or use the single switch upstairs to control both the stairway and downstairs lights.  Currently, there is no neutral wire in the box for the upstairs switch, but there appears to be a neutral in the downstairs box.  I am wondering whether I could use the traveler running to the upstairs box as a netural wire running to the netural wire in the downstairs box.  My question is whether it would be possible, once I ran the netural wire upstairs, to use your 3 switches to enable me to turn off the downstairs lights both from the upstairs and downstairs switches.  In this configuration, there would be no traveler wire.  Could I make it work?  What equipment should I buy?  And how would I wire it?