function show_categs(num)
{
    if(num == 3) {
		if(getObject('cat1') != null) getObject('cat1').disabled = false;
		if(getObject('cat2') != null) getObject('cat2').disabled = false;
		if(getObject('cat3') != null) getObject('cat3').disabled = false;
	}
    if(num == 2) {
		if(getObject('cat1') != null) getObject('cat1').disabled = false;
		if(getObject('cat2') != null) getObject('cat2').disabled = false;
		if(getObject('cat3') != null) getObject('cat3').disabled = true;
	}
    if(num == 1) {
		if(getObject('cat1') != null) getObject('cat1').disabled = false;
		if(getObject('cat2') != null) getObject('cat2').disabled = true;
		if(getObject('cat3') != null) getObject('cat3').disabled = true;
	}
    if(num == 0) {
		if(getObject('cat1') != null) getObject('cat1').disabled = true;
		if(getObject('cat2') != null) getObject('cat2').disabled = true;
		if(getObject('cat3') != null) getObject('cat3').disabled = true;
	}
}

function getObject( id )
{
    if (document.getElementById)
        var returnVar = document.getElementById(id);
    else if (document.all)
        var returnVar = document.all[id];
    else if (document.layers)
        var returnVar = document.layers[id];
    return returnVar;
}