in javascript -- how do you call this code from server-side (aspx)

function calculateTheNewMortgage() 
{
    // Calculate LTV     
         
    var EstimatedValuationAmount   = parseInt(document.getElementById('TextBox_EstimatedValuationAmount').value);
 
    if( isNaN(EstimatedValuationAmount) )
    EstimatedValuationAmount = 1;     
        
    var OutstandingAmount1stCharge = parseInt(document.getElementById('TextBox_OutstandingAmount1stCharge').value);
    
    if( isNaN(OutstandingAmount1stCharge) )
    OutstandingAmount1stCharge = 0;
    
    var OutstandingAmount2ndCharge = parseInt(document.getElementById('TextBox_OutstandingAmount2ndCharge').value);
    
    if( isNaN(OutstandingAmount2ndCharge) )
    OutstandingAmount2ndCharge = 0;
    
    var OutstandingAmount3rdCharge = parseInt(document.getElementById('TextBox_OutstandingAmount3rdCharge').value);
    
    if( isNaN(OutstandingAmount3rdCharge) )
    OutstandingAmount3rdCharge = 0;
        
    var ExtraMoneyHowMuch          = parseInt(document.getElementById('TextBox_ExtraMoneyHowMuch').value);
 
    if( isNaN(ExtraMoneyHowMuch) )
    ExtraMoneyHowMuch = 0;
           
    var OutstandingAmountsTotal = OutstandingAmount1stCharge
                                + OutstandingAmount2ndCharge 
                                + OutstandingAmount3rdCharge 
                                + ExtraMoneyHowMuch;
    
    var LTVSubTotal = OutstandingAmountsTotal / EstimatedValuationAmount;
    
    var LTV = LTVSubTotal * 100;
    var LTVTotal = round_decimals(LTV, 2)
    
    document.getElementById('TextBox_LTV').value = LTVTotal;
    
    // Calculate Total Loan Required
    
    var HowMuch1stCharge = parseInt(document.getElementById('TextBox_HowMuch1stCharge').value);
    
    if( isNaN(HowMuch1stCharge) )
    HowMuch1stCharge = 0;
    
    var HowMuch2ndCharge = parseInt(document.getElementById('TextBox_HowMuch2ndCharge').value);
    
    if( isNaN(HowMuch2ndCharge) )
    HowMuch2ndCharge = 0;
    
    var HowMuch3rdCharge = parseInt(document.getElementById('TextBox_HowMuch3rdCharge').value);
    
    if( isNaN(HowMuch3rdCharge) )
    HowMuch3rdCharge = 0;
    
    var TotalLoanRequired = OutstandingAmount1stCharge 
                          + OutstandingAmount2ndCharge 
                          + OutstandingAmount3rdCharge 
                          + HowMuch1stCharge 
                          + HowMuch2ndCharge 
                          + HowMuch3rdCharge 
                          + ExtraMoneyHowMuch;
    
    document.getElementById('TextBox_LoanRequired').value = TotalLoanRequired;
}
 
function round_decimals(original_number, decimals) 
{
    var result1 = original_number * Math.pow(10, decimals)
    var result2 = Math.round(result1)
    var result3 = result2 / Math.pow(10, decimals)
    
    return pad_with_zeros(result3, decimals)
}
 
function pad_with_zeros(rounded_value, decimal_places) 
{
    var value_string = rounded_value.toString()
    var decimal_location = value_string.indexOf(".")
 
    if (decimal_location == -1) 
    {
        decimal_part_length = 0
        value_string += decimal_places > 0 ? "." : ""
    }
    else 
    {
        decimal_part_length = value_string.length - decimal_location - 1
    }
    
    var pad_total = decimal_places - decimal_part_length
    
    if (pad_total > 0) 
    {
        for (var counter = 1; counter <= pad_total; counter++) 
            value_string += "0"
    }
    return value_string
}

<div class="cssbox_body_fb" style="text-align: left">
                    <span style="font-family: Verdana"><span style="color: black">
                        <span style="font-size: 10pt; font-family: 'Arial Unicode MS'">
                    <span lang="en-gb">L</span>ooking for any
                            extra money other than to consolidate any loans or outstanding credit ?<b>
                    <span lang="en-gb">&nbsp; </span></b>&nbsp;
                        <asp:RadioButton ID="RadioButton_ExtraMoneyNo" runat="server" Font-Names="Arial Unicode MS"
                            Font-Size="9pt" GroupName="ExtraMoney" Text="No" Checked="True" 
                        AutoPostBack="True" 
                        oncheckedchanged="RadioButton_ExtraMoneyNo_CheckedChanged" />
                    <span lang="en-gb">&nbsp;</span><asp:RadioButton ID="RadioButton_ExtraMoneyYes" 
                        runat="server" Font-Names="Arial Unicode MS"
                            Font-Size="9pt" GroupName="ExtraMoney" Text="Yes" 
                        AutoPostBack="True" 
                        oncheckedchanged="RadioButton_ExtraMoneyYes_CheckedChanged1" />
                    <br />
                    </span>
                    <asp:Panel ID="Panel_ExtraMoney" runat="server" Visible="False">
                        <span style="font-family: Verdana"><span style="color: black">
                        <span style="font-size: 10pt; font-family: 'Arial Unicode MS'">
                        <br />
                        </span><span style="font-size: 10pt">
                        <span style="font-family: '@Arial Unicode MS'">How much&nbsp; £ </span></span>
                        <asp:TextBox ID="TextBox_ExtraMoneyHowMuch" 
    runat="server" Font-Names="Arial Unicode MS"
                            Font-Size="9pt" Width="70px" MaxLength="10" 
                        onchange="calculateTheNewMortgage()" 
                        onkeypress="return numeralsOnly(event)" 
    CssClass="RightToLeftBox"></asp:TextBox>
                        <span lang="en-gb">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
                        <span style="font-size: 10pt; font-family: 'Arial Unicode MS'">Purpose of Loan&nbsp;</span>
                        <asp:DropDownList ID="DropDownList_PurposeOfLoan"
                                runat="server" 
    DataSourceID="SqlDataSource_PurposeOfLoan" DataTextField="PurposeOfLoanName"
                                DataValueField="PurposeOfLoan_ID" Font-Names="Arial Unicode MS" 
                        Font-Size="9pt">
                        </asp:DropDownList>
                        </span>
                        <br />
                        </span></span>
                    </asp:Panel>
                        <br />
                    </span></span>
                </div>