Select Boxes :: Write A Function Called "add" To Move Elements From The 1st Box To The Second?

I have 2 select boxes which are separated by the buttons "Choose" and "Remove"I have populated the 1st Select Box with 10 elements. I want the elements to move over to the 2nd Select Box when the user clicks "Choose"I have given the 1st Select Box an id of "firstBox," and the 2nd Select Box has an id of "secondBox"I am trying to write a function called "add" to move elements from the 1st box to the second. So far I have:

function add()
{
var y=document.getElementById("secondBox")
var x=document.getElementById("firstBox");[code].....

Still the elements from the first box are non populating in the second box.I have played around with "appendChild" but I cannot get that to work either.