function doit(topSelector, childrenSelector, itemsName)
{
    var s1 = document.all[topSelector];
    var s2 = document.all[childrenSelector];
	var items = eval(itemsName);
    s2.options.length = 0; // clear all
    var topSelected = items[s1.selectedIndex];
    if(topSelected == null)
    	return;
    var len = topSelected.length;
    s2.options.length = len;
    for(var i = 0; i < len; i++)
    {
        s2.options[i] = items[s1.selectedIndex][i];
    }
    s2.selectedIndex = 0; //reset the selected to first one
}