Activating a command by adding a redstone current?

I have worked for a tiny bit on Computercraft when trying to make a Elevator (with a call back). For example, all I needed to do was type 3-2 which the elevator is called up to floor 3 and brings me to floor 2 and then goes back down to the bottom floor. I want to see if I can make this simpler by only the use of a button.

Is there a way to activate and run a program by sending a redstone current to the computer?
I'd like to place buttons on the walls on my elevator, when I press the button (a sign will say 2) the elevator would go up to floor 2 (framemotors).
I'm a novice at this and wrote a code for each floor 1-2, 1-3, 1-4, 2-1, 2-2, etc.

So by pressing the button it reaches the computer(say the left side) it activates a program that makes the elevator work so there is NO typing a command to get it to work, as the button does it for you.

Is this possible? If so, please share how you do it.
Thanks

you can use os.pullEvent() to wait until it recieves redstone, then check if its on, and if it is then activate the elevator.

-- put this in startup
while true do
 local event, parameter = os.pullEvent("redstone")
 if redstone.getInput("left") then
  shell.run("1-2")
 end
end

Also, this belongs in the Ask a Pro section.

os.pullEvent("redstone")
then an if statement checking if the redstone is on
EDIT:
:D/>/>

awesome , this is a big help!

General use of eventlistener:

local pullEvent = os.pullEventRaw
local e, p1, p2, p3, p4, p5 = pullEvent(--[[ filter. None means no filter ]])
-- Handle event. Example of a simple key press handler:
if e == "key" then
  print(p1 .. " = " .. string.char(p1))
end