ChangeSelectedValue of a Select event

ChangeSelectedValue of a Select event

How may I fire an event when I change the selected value of a the tag
<select> using JavaScript ?
I tried something like this, but I'm lost now ;s I want to change the
value of a label when I change the selected value of the <select> tag.
function ChangeSelectValue(ddlID, value, change) {
var ddl = document.getElementById(ddlID);
}