function updatecat()
{
	//clear cat
	for(index=0; index < 9; index++)
	{
		document.chooseCategory.cat.options[index].text = '';
		document.chooseCategory.cat.options[index].value = '';
	}

	document.chooseCategory.cat.options[0].selected = true;

whichSelected = document.chooseCategory.parentCat.selectedIndex;
	if(document.chooseCategory.parentCat.options[whichSelected].value == '253')
	{
	
		document.chooseCategory.cat.options[0].value = '420';
		document.chooseCategory.cat.options[0].text = 'Canyon';
	
		document.chooseCategory.cat.options[1].value = '261';
		document.chooseCategory.cat.options[1].text = 'Envoy';

		document.chooseCategory.cat.options[2].value = '332';
		document.chooseCategory.cat.options[2].text = 'Sierra';

		document.chooseCategory.cat.options[3].value = '268';
		document.chooseCategory.cat.options[3].text = 'Yukon & Denali';

		document.chooseCategory.cat.options[4].value = '267';
		document.chooseCategory.cat.options[4].text = 'Sonoma';
		
		

	}

	if(document.chooseCategory.parentCat.options[whichSelected].value == '254')
	{
		
		document.chooseCategory.cat.options[0].value = '299';
		document.chooseCategory.cat.options[0].text = 'Silverado';
		
		document.chooseCategory.cat.options[1].value = '295';
		document.chooseCategory.cat.options[1].text = 'Avalanche';

		document.chooseCategory.cat.options[2].value = '298';
		document.chooseCategory.cat.options[2].text = 'S-10';

		document.chooseCategory.cat.options[3].value = '296';
		document.chooseCategory.cat.options[3].text = 'Blazer';

		document.chooseCategory.cat.options[4].value = '305';
		document.chooseCategory.cat.options[4].text = 'Camaro';
		
		document.chooseCategory.cat.options[5].value = '412';
		document.chooseCategory.cat.options[5].text = 'Colorado';		

		document.chooseCategory.cat.options[6].value = '301';
		document.chooseCategory.cat.options[6].text = 'Suburban';

		document.chooseCategory.cat.options[7].value = '302';
		document.chooseCategory.cat.options[7].text = 'Tahoe';

		document.chooseCategory.cat.options[8].value = '303';
		document.chooseCategory.cat.options[8].text = 'Tracker';

		//document.chooseCategory.cat.options[9].value = '304';
		//document.chooseCategory.cat.options[9].text = 'Trailblazer';

	}

	return true;
}