Telerik RadNumericTextBox not returning updated value which is set from client side javascript

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VB

ASP.NET

Javascript

Telerik

i have created a RadNumericTextBox inside a Talerik Rad Grid Edit form template as below:

<telerik:RadNumericTextBox ID="rdtbTPCCommissionAmount" DataType="System.Decimal"
                                                EnabledStyle-HorizontalAlign="Right" Type="Number" NumberFormat-DecimalDigits="2"
                                                ReadOnly="true" AutoPostBack="false" CssClass="amountDueWidth disableInputStyle"
                                                runat="server" NumberFormat-AllowRounding="true" Style="width: 100% !important;"
                                                Width="100%">
                                                <IncrementSettings InterceptMouseWheel="false" InterceptArrowKeys="false" />
                                            </telerik:RadNumericTextBox></pre
On a another RadNumericTextBox blur event i calling a Javascript funtion as below:
<pre lang="xml">function validateThirdPartyCommissionRate(){
               validateThirdPartyRate("<%= rgThirdPartyCommissions.ClientID %>");
           }

From this above funtion i am calling a method written in JS file like below and setting some value to that RadNumericTextBox:

function validateThirdPartyRate(radGridId) {
    var grid = $find(radGridId).get_element();
    var commissionAmt = $telerik.findElement(grid, "rdtbTPCCommissionAmount");

var calculatedAmount = parseFloat(rate) * parseFloat(premiumFeeAmt) / 100;
           commissionAmt._setNewValue(calculatedAmount);
           $("#ctl00_cphMainContentPage_rgThirdPartyCommissions_ctl00_ctl07_rdtbTPCCommissionAmount").val = calculatedAmount;
           commissionAmt._value = calculatedAmount.toFixed(2);
           commissionAmt._text = calculatedAmount.toFixed(2);
           commissionAmt.value = calculatedAmount
}

I have used all diffrent property/methods to set the value some of them are setting the value on UI but when i tried to DirectCast this control on serverside it gives me it's old value not the updated which i set from Javascript just like above.

commissionAmt = DirectCast(editedItem.FindControl("rdtbTPCCommissionAmount"), RadNumericTextBox).Text

So suggestion will be welcome to to fix this issue?