function validate_required(field,alerttxt){
with (field)
{
if (value==null||value=="")
  {alert(alerttxt);return false}
else {return true}
}
}
function validate_form(thisform)
{ 
with (thisform)
{
if (validate_required(details,"Please send us details of your travel requirements.")==false)
  {details.focus();return false}
if (validate_required(name,"Please tell us your name.")==false)
  {name.focus();return false}
if (validate_required(email,"Please provide a valid email address.")==false)
  {email.focus();return false}
}
}