Changing Selected Text Of Dropdownlist In Gridview Using Javascript

I have a dropdownlist, and a Gridview where one of the columns is a dropdownlist. both dropdown lists use the same data source. When a value is selected in the dropdownlist (outside the gridview) I want to chaneg the selectedValue and selectText of every dropdownlist in my gridview. This is what I have tried:

Dropdownlist:
<asp:DropDownList onclick="javascript:onJDSelection()" ID="DropDownList3" runat="server"
DataSourceID="SqlDataSource4" DataTextField="circt_cstdn_nm"
DataValueField="circt_cstdn_user_id">
Javascript:
<script type="text/javascript">
function onJDSelection() {
var jd = document.getElementById('DropDownList3.ClientID').selectedText;
var grid = document.getElementById('GridView2.ClientID');
//Loop starts from 1 because the zeroth row is the header.
for (var i = 1; i < grid.rows.length; i++) {
var OtherText = grid.rows[i].cells[2].innerText; // Works fine
grid.rows[i].cells[3].getElementsById('ddl_JD').selectedText = jd;
}
}

When I click I get an error. It says object expected. However I know those objects exsist!