function valid_email(email) {
 var filter  = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
 if (filter.test(email)) {
  return true;
 } else {
  return false;
 }
}
function check_form() {
if (!document.referral.ReferringPhysician.value) {
 alert('One or more mandatory fields are empty. All fields with a red * are required.');
 return false;
}
if (!document.referral.PracticeName.value) {
 alert('One or more mandatory fields are empty. All fields with a red * are required.');
 return false;
}
if (!document.referral.PracticePhone.value) {
 alert('One or more mandatory fields are empty. All fields with a red * are required.');
 return false;
}
if (!document.referral.CallersName.value) {
 alert('One or more mandatory fields are empty. All fields with a red * are required.');
 return false;
}
if (!valid_email(document.referral.CallersEmail.value)) {
 alert('One or more mandatory fields are empty. All fields with a red * are required.');
 return false;
}
if (!document.referral.PatientName.value) {
 alert('One or more mandatory fields are empty. All fields with a red * are required.');
 return false;
}
if (!document.referral.DOB.value) {
 alert('One or more mandatory fields are empty. All fields with a red * are required.');
 return false;
}
if (!document.referral.Address1.value) {
 alert('One or more mandatory fields are empty. All fields with a red * are required.');
 return false;
}
if (!document.referral.City.value) {
 alert('One or more mandatory fields are empty. All fields with a red * are required.');
 return false;
}
if (!document.referral.St.value) {
 alert('One or more mandatory fields are empty. All fields with a red * are required.');
 return false;
}
if (!document.referral.Zip.value) {
 alert('One or more mandatory fields are empty. All fields with a red * are required.');
 return false;
}
if (!document.referral.WorkPhone.value) {
 alert('One or more mandatory fields are empty. All fields with a red * are required.');
 return false;
}

}