function validate(aform, mailto, mailtopic) {
if ((aform["Name"].value.length==0) || (aform["Name"].value==null)) {
  alert("Please fill in your name");
  return false;
}
if ((aform["email"].value.length==0) || (aform["email"].value==null)) {
  alert("Please fill in your e-mail address");
  return false;
}
if ((aform["Telephone"].value.length==0) || (aform["Telephone"].value==null)) {
  alert("Please fill in your telephone number");
  return false;
}
var i=aform["Riding"].selectedIndex;
aform["Riding"].options[i].value=aform["Riding"].options[i].text;
alert("Thanks for your interest!");
sendEmail(aform, mailto, mailtopic);
}