--Woodcraft stores sell a remote on/off switch for just this
purpose. It clips to a pocket, so it's real handy. Can't remember cost but
it was pretty reasonable.
--As for controlling specific gates in a series of ducts there is
an electric gate system on the market but it's *really* pricey, plus I
think the idea of an electrically-controlled device in an area where
static might be a problem is a Bad Idea. I run my gates with pneumatics;
costs about $50.- per gate in parts. You'll need a pneumatic toggle
switch, some tubing, a double-acting cylinder with about 4" travel and of
course a source of compressed air. Looks kinda silly but works really
neat.

--
"Steamboat Ed" Haas : Just another fart in
Hacking the Trailing Edge! : the Elevator of Life...
http://www.nmpproducts.com/intro.htm
---Decks a-wash in a sea of words---