Hi everyone. Hope someone can help.

I have a page with a asp.net textbox on it where the user can specify a quantity for an item they are ordering. I also have a asp.net label which displays the subtotal. When the user changes the value in the quantity textbox I want the subtotal to update. I know how to do the calculation etc but I can't figure out how to call a function to do the calculation as soon as the value in the textbox changes.

It works if i use the onTextChanged event and click off the textbox when the quantity has been changed but I want it to happen when the contents on the textbox change.

I have searched the forums for help and have managed to figure out that I need to use javascript but am not sure how to do it. I think I need to call the javascript function using the onchange event but then how do I update the subtotal label?

I think the best you can do is handle the onblur event.  This will trigger when the focus is lost from the textbox.

Edit: You can also use the onchange event, which will only trigger if the text is actually changed, otherwise it doesn't trigger.

Try this:

<asp:TextBox ID="TextBox1" runat="server" onchange="textBox1OnChange(this);"></asp:TextBox>

<!-- Use a TextBox that looks like a Label since otherwise, if the page does a PostBack the values will be lost -->
<asp:TextBox id="TextBox1Label" BorderColor="White" BorderStyle="None" BorderWidth="0" runat="server"></asp:TextBox>

<script type="text/javascript">
<!--
function buttonOnClick(elementRef)
{
 var labelId = elementRef.id + 'Label';

 // Do the calculations here...
 var calculatedValue = elementRef.value;

 document.getElementById(labelId).value = calculatedValue;
}

// Need to set the readOnly property here, since setting it in the markup does not persist client-side changes.
function windowOnLoad()
{
 document.getElementById('<%= TextBox1Label.ClientID %>').readOnly = true;
}

window.onload = windowOnLoad;
// -->
</script>

NC...