function checkZip(field){
	var allowedOnes = "0123456789"
	if (field.value.length != 5)
	{
		return false;
	}
	for (i=0; i < field.value.length; i++)
	{
		zipSearch = field.value.substr(i,1)
		if (allowedOnes.indexOf(zipSearch) == -1)
		{
			return false;
		}
	}
	return true
}