Fire textchanged event in javascript asp.net c#

Question

in my application, I used asp.net Repeater with table to populate item from database and DropDownExtender of Ajax. When user clicks on textbox, data with html data've been shown.Now I want to fire textchanged event of textbox when data row is selected. I bind data to repeater in page_load.
Thanks All

What I have tried:

in javascript
function SetValue(value) {
var DropdownList = document.getElementById("<%=ddlItemID.ClientID %>");
// txtFriend.value = value;
alert(value);
}
at repeater, I tried like this

<asp:Repeater ID="rptr" runat="server">

<HeaderTemplate>

<table style="border: 1px solid black;" >

<tr style="border: 1px solid black;">

<th style="border: 1px solid black;">

ID

</th>

<th style="border: 1px solid black;">

Unit

</th>

<th style="border: 1px solid black;">

Price

</th>

</tr>

</HeaderTemplate>

<ItemTemplate>

<tr onclick="SetValue('<%#Eval("ID")%>')" style="cursor: hand" onmouseover="style.backgroundColor='#bfb9b9'"

onmouseout="style.backgroundColor=''" style="border: 1px solid black;">

<td style="border: 1px solid black;">

<%#Eval("ID")%>

</td>

<td style="border: 1px solid black;">

<asp:Label ID="lbFirstName" Text='<%#Eval("Unit")%>' runat="server" />

</td>

<td style="border: 1px solid black;">

<asp:Label ID="lblLastName" Text='<%#Eval("Price")%>' runat="server" />

</td>

</tr>

</ItemTemplate>

<AlternatingItemTemplate>

<tr onclick="SetValue('<%#Eval("ID")%>')" style="cursor: hand" onmouseover="style.backgroundColor='#fff4f4'"

onmouseout="style.backgroundColor=''" style="border: 1px solid black;">

<td style="border: 1px solid black;">

<%#Eval("ID")%>

</td>

<td style="border: 1px solid black;">

<asp:Label ID="lbFirstName1" Text='<%#Eval("Unit")%>' runat="server" />

</td>

<td style="border: 1px solid black;">

<asp:Label ID="lblLastName1" Text='<%#Eval("Price")%>' runat="server" />

</td>

</tr>

</AlternatingItemTemplate>

<FooterTemplate>

</table>

</FooterTemplate>

</asp:Repeater>