Dynamic Text Boxes

i have been asked to create text boxes dynamically on a web site, the user can click a button and a new set of text boxes will appear. The user can add as many boxes as many times as he wants, I have created the text boxes already using the following code.

function inserttextboxs() {
var tab = document.getElementById("Difference")

var tr = tab.insertRow()
var tc = tr.insertCell("") tc.innerHTML = '< input type=text id=text1 name=text1>';

}

The problem is I don't if this how I should be doing it when I submit the form all the elements have the same id, I need to create something with unique id's so I can retrieve the different values