Something

<html><head><script language="JavaScript" type="text/javascript">  var days;  var cost;  var weight;  var tax;  var total;  days = document.forms['reservations'].elements['days'];  cost = document.forms['reservations'].elements['cost'];  weight = document.forms['reservations'].elements['weight'];  weight.value = '250lbs.';  if(cost.value == ''){cost.value = 0 + ' $';}  tax = document.forms['reservations'].elements['tax'];  total = document.forms['reservations'].elements['total'];  if(tax.value == ''){tax.value = 0 + ' $';}  if(total.value == ''){total.value = 0 + ' $';}/*function init(){  days = document.forms['reservations'].elements['days'];  cost = document.forms['reservations'].elements['cost'];  weight = document.forms['reservations'].elements['weight'];  weight.value = '250lbs.';  if(cost.value == ''){cost.value = 0 + ' $';}  tax = document.forms['reservations'].elements['tax'];  total = document.forms['reservations'].elements['total'];  if(tax.value == ''){tax.value = 0 + ' $';}  if(total.value == ''){total.value = 0 + ' $';}  }*/function doTheMath(x){ if(x == 1){  cost.value = 25 * days.value + ' $'; } if(x == 2){  cost.value = 30 * days.value + ' $'; } if(x == 3){  cost.value = 35 * days.value + ' $'; } var taxvalue = parseFloat(parseFloat(cost.value) * 6.5)/100; tax.value = taxvalue.toFixed(2) + ' $'; var totalvalue = parseFloat(cost.value) + parseFloat(tax.value); total.value = totalvalue.toFixed(2)  + ' $';}function checkstate(){ if (days.value != ''){  if(document.forms['reservations'].sc_model.value == 'disc'){doTheMath(1);}  if(document.forms['reservations'].sc_model.value == 'dist'){doTheMath(2);}  if(document.forms['reservations'].sc_model.value == 'dipl'){doTheMath(3);} }}function doWeight(){ if(document.forms['reservations'].sc_model.value == 'disc') document.forms['reservations'].elements['weight'].value = '250lbs.'; if(document.forms['reservations'].sc_model.value == 'dist') document.forms['reservations'].elements['weight'].value = '250lbs.'; if(document.forms['reservations'].sc_model.value == 'dipl') document.forms['reservations'].elements['weight'].value = '300lbs.';}//window.onload = init;</script></head><body><form method="POST" action="sendmail.php" name="reservations"><table><tr> <td class="style2">  <select name="sc_model" onChange="doWeight();">   <option value="disc">Discovery SUV</option>   <option value="dist">Distinction SUV</option>   <option value="dipl">Diplomat SUV</option>  </select> </td> <td class="style2"><INPUT TYPE="TEXT" SIZE="7" NAME="weight" class="disabled"></td> <td class="style2" align="center"><p><INPUT TYPE="TEXT" SIZE="3" NAME="days" onKeyUp="checkstate();"></p></td> <td class="style2" align="center"><p><INPUT TYPE="TEXT" SIZE="7" NAME="cost" class="disabled"></p></td></tr><tr> <td class="style2" colspan="3"><p>6.5% Sales Tax</p></td> <td class="style2" align="center"><p><INPUT TYPE="TEXT" SIZE="7" NAME="tax" class="disabled"></p></td></tr><tr> <td class="style2" colspan="3"><p>Total</p></td> <td class="style2" align="center"><p><INPUT TYPE="TEXT" SIZE="7" NAME="total" class="disabled"></p></td></tr></table></form></body></html>