Left & Right navigation

hiya, im trying to create a site where on clicking seperate left and right buttons they will move along a background image a set distance. ive drawn a picture to help:

for example the background image would be 2000px by 300px, the dotted box would be the screen size say 400px in length

when the right button was pressed i would like the screen to shift 400px to the right, which would then show a new part of the background.

would it look something like:

Right_Button.onRelease = function()
{
_root.destX = 400px
_root.destY = 0
}

and the left:

Left_Button.onRelease = function()
{
_root.destX = -400px
_root.destY = 0
}

also how would you make it so its a smooth transition? and what happens when it gets to the end

sorry for all the questions on my first post,

Phil