problem with textbox value

Last time, please try such small things by yourself instead of asking questions here. You need to learn and make some effort.

Steps for your thing:
1. Define a onblur or onfocusout event for the textbox1 (if server control then add through attributes)
2. Define the related method in JavaScript
3. In this method, get the value of textbox1 and then based on it set the value in textbox2

You might need to know:
How to access textbox value in JS:

document.getElementById("textbox1").value

How to add attribute via code:

textbox1.Attributes.Add("onblur","javascript: GetT1ValueAndSetT2(this);");

So overall,
HTML:

<asp:TextBox ID="txtValue1" runat="server" ></asp:TextBox>
<asp:TextBox ID="txtValue2" runat="server"  ></asp:TextBox>

and Javascript

<script type="text/javascript">
  function GetT1ValueAndSetT2(txtValue1)
  {
     document.getElementById("txtValue2").value=parseFloat(txtValue1.value,10)*5;
  }

</script>

Try now.

Hi,

You can use jquery to solve the issue. Try this solution below,

<script  type="text/javascript" src="http://code.jquery.com/jquery-1.9.1.min.js"></script>
<script type="text/javascript">
    $(document).ready(function () {

        $("input[type='text']:eq(0)").keyup(function () {
            var txtVal = $("input[type='text']:eq(0)").val();
            var calculated = parseInt(txtVal) * 10;
            $("input[type='text']:eq(1)").val(calculated);

        });
    });
</script>

And here is your TextBox's

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>

Hope this will help.