Form auto fill help

[Clinton]

I have a form. If I put in 5 for 'Quantity' and '1.00' for UnitCost when I go to TotalCost I want it to automatically compute the total. In this case 5.00. Make sense? How do I do this?

 

<tr><td>Quantity:</td><td>
<input type="text" name="Quantity">
</td></tr>
<tr><td>Unit Cost:</td><td>
<input type="text" name="UnitCost">
</td></tr>
<tr><td>Total Cost:</td><td>
<input type="text" name="TotalCost">
</td></tr>

[ToonMariner]

html...

 

<tr><td>Quantity:</td><td>
<input type="text" name="Quantity" id="Quantity">
</td></tr>
<tr><td>Unit Cost:</td><td>
<input type="text" name="UnitCost" id="UnitCost">
</td></tr>
<tr><td>Total Cost:</td><td>
<input type="text" name="TotalCost" id="TotalCost" onfocus="calcCost();">
</td></tr>

 

javscript to be placed in the head section.

 

function calcCost()

{

var num = document.getElementById('Quantity').value;

var cost = document.getElementById('UnitCost').value;

document.getElementById('TotalCost').value =  num * cost;

}