parsing xml file with dtd

[Mary Connolly]

I have an external dtd for a xml file. When the xml file is viewed there are no errors it seems to work okay with the dtd. However, when I go to parse the xml file using dom I am getting a SAX exception. If I do not reference the dtd in the xml file the parsing completes sucessfully. Does anyone know what I am doing wrong??? thanx
public class Diagnose
{ public String getNormValue(String sBloodGroup,
String sBloodTest, String sAgeGroup)
{ DocumentBuilderFactory dbf = null;
DocumentBuilder db = null;
Document doc = null;
try { File NormsFile = new File
("c:\\project\\BloodResults\\blood_norms.xml");
dbf = DocumentBuilderFactory.newInstance();
db = dbf.newDocumentBuilder();
dbf.setIgnoringComments(true); // We went to ignore comments
//dbf.setValidating(true); // validate DTD
doc = db.parse(NormsFile);