function setOnderwerkOnChange(select_o)
{
	document.getElementById('adres_tr').style.display = 'none';
	document.getElementById('postcode_tr').style.display = 'none';
	document.getElementById('plaats_tr').style.display = 'none';

	var value_u = select_o.options[select_o.selectedIndex].value;
	var required_s = document.reageren_form.__required_fields__.value;

	document.reageren_form.__required__.value = required_s;

	if (value_u == 'Post')
	{
		document.getElementById('adres_tr').style.display = '';
		document.getElementById('postcode_tr').style.display = '';
		document.getElementById('plaats_tr').style.display = '';

		document.reageren_form.__required__.value = required_s + ', adres, postcode, plaats';
	}
}