Llenado Select con Javascript

[fmb1982]

No jala.... :(

Código HTML:

<script type="text/javascript">
function grad() {
var grado=new array();
var univer=new array();
grado[0] = new Option("Primera Grado","Primer Grado","defaultSelected","selected")
grado[1] = new Option("Segundo Grado","Segundo Grado","defaultSelected","selected")
grado[2] = new Option("Tercer Grado","Tercer Grado","defaultSelected","selected")
grado[3] = new Option("Cuarto Grado","Cuarto Grado","defaultSelected","selected")
grado[4] = new Option("Quinto Grado","Quinto Grado","defaultSelected","selected")
grado[5] = new Option("Sexto Grado","Sexto Grado","defaultSelected","selected")
univer[0] = new Option("Cursando","Cursando","defaultSelected","selected")
univer[1] = new Option("Egresado","Egresado","defaultSelected","selected")

if (document.getElementById("niv_usr").value=="Kinder")
{
	for (i=0;i<=2;i++)
	{
	document.getElementById("grad_usr").options = grado[i]; 
	}	
}

if (document.getElementById("niv_usr").value=="Primaria")
{
	for (i=0;i<=5;i++)
	{
	document.getElementById("grad_usr").options = grado[i] 
	}	
}

if (document.getElementById("niv_usr").value=="Secundaria")
{
	for (i=0;i<=2;i++)
	{
	document.getElementById("grad_usr").options = grado[i]; 
	}	
}

if (document.getElementById("niv_usr").value=="Bachillerato")
{
	for (i=0;i<=5;i++)
	{
	document.getElementById("grad_usr").options = grado[i]; 
	}	
}

if (document.getElementById("niv_usr").value=="Universidad")
{
	for (i=0;i<=1;i++)
	{
	document.getElementById("grad_usr").options = univer[i]; 
	}
}
}
</script>