please can anyone tell me why this script doesnt seem to work.thankz
<script>
function calculate (){
var age = document.getElementById('age');
var amt = document.getElementById('amount');
var plan = document.getElementById('plan');
var ben1 = document.getElementById('benefit1');
var ben2 = document.getElementById('benefit2');
var yrs = document.getElementById('length');
var ap = (amt.value/yrs.value)+Math.pow((100*Math.sqrt(age.value/(55*yrs.value))),2);
document.write('annual premium'+ap);
}
function checkplan(){
var plan = document.getElementById('plan');
var age = document.getElementById('age');
var but = document.getElementById('calculate');
if (plan.value == 5){
yrs.disabled = false;
}
else if (plan.value == 4){
yrs.value = 25;
if((age.value + 25)>60){
alert("The maximum age allowed for this policy at maturity is 60.Please choose another Policy");
calculate.disabled = true;
}
}
else if (plan.value == 3){
yrs.value = 20;
if((age.value + 20)>60){
alert("The maximum age allowed for this policy at maturity is 60.Please choose another Policy");
calculate.disabled = true;
}
}
else if (plan.value == 2){
yrs.value = 15;
if((age.value + 15)>60){
alert("The maximum age allowed for this policy at maturity is 60.Please choose another Policy");
calculate.disabled = true;
}
}
else if (plan.value == 1){
yrs.value = 10;
if((age.value + 10)>60){
alert("The maximum age allowed for this policy at maturity is 60.Please choose another Policy");
calculate.disabled = true;
}
}
}
function checkyear(){
var yrs = document.getElementById('length');
var age = document.getElementById('age');
if((yrs.value+age.value) >60) {
alert("The maximum age allowed for this policy at maturity is 60.Please choose another Policy");
calculate.disabled = true;
}
}
</script>
</head>
<body>
<form action="" method="post" name="secure"><table width="514" height="158" border="0" cellpadding="0" cellspacing="0">
<tr align="center">
<td width="276" height="30"><span id="sprytextfield1">
<label>Name:
<input type="text" name="name" id="name" accesskey="n" tabindex="1" />
</label>
<span class="textfieldRequiredMsg">A value is required.</span></span></td>
<td width="224"><span id="sprytextfield2">
<label>Age:
<input type="text" name="age" id="age" />
</label>
<span class="textfieldRequiredMsg">A value is required.</span></span></td>
</tr>
<tr align="center">
<td height="29"><span id="sprytextfield3">
<label>Cover Amount:
<input type="text" name="amount" id="amount" />
</label>
<span class="textfieldRequiredMsg">A value is required.</span></span></td>
<td> </td>
</tr>
<tr align="center">
<td height="34"><label>Plan:
<select name="plan" id="plan" onblur="checkplan();">
<option value="0">none</option>
<option value="1">money back 10</option>
<option value="2">money back 15</option>
<option value="3">money back 20</option>
<option value="4">money back 25</option>
<option value="5">whole life</option>
</select>
</label></td>
<td><label>
<input type="checkbox" name="benefit1" id="benefit1" />
Term Rider </label><label><input name="benefit2" type="checkbox" id="benefit2" />Critical Illness</label></td>
</tr>
<tr align="center">
<td height="37"><span id="sprytextfield4">
<label>Length of Cover (Yrs):
<input name="length" type="text" disabled="true" id="length" onblur="checkyear();"/>
</label>
<span class="textfieldRequiredMsg">A value is required.</span></span></td>
<td><label>
<input type="button" name="calculate" id="calculate" value="Calculate" onclick="calculate();"/>
</label></td>
</tr>
<tr align="center">
<td><span id="sprytextfield5">
<label>Monthly Premium:
<input name="mpremium" type="text" disabled="disabled" id="mpremium" />
</label>
<span class="textfieldRequiredMsg">A value is required.</span></span></td>
<td><span id="sprytextfield6">
<label>Annual Premium
<input name="apremium" type="text" disabled="disabled" id="apremium" />
</label>
<span class="textfieldRequiredMsg">A value is required.</span></span></td>
</tr>
<tr align="center">
<td><span id="sprytextfield7">
<label>Bonus at Maturity:
<input name="bonus" type="text" disabled="disabled" id="bonus" />
</label>
<span class="textfieldRequiredMsg">A value is required.</span></span></td>
<td></td>
</tr>
</table>
</form>
</body>