jquery launch a button click event

Question

I am very new to jquery and javascript.So I have an aspx page with a button. Clicking that opens a jquery dialog. This dialog is a div. This div contains some controls,textboxes and 2 ASP image buttons. I have to use image buttons. Clicking that should launch the code on my .vb page.

My Html
<div id="divModal" title="Enter Truck Details" style="width:100px;">
<table><tr><td>
<asp:ImageButton ID="btnAdd" runat="server" OnCommand="btnAdd_Command"   ImageUrl="~/internal/images/add.gif" /> <br />
<asp:ImageButton ID="bntCancel" runat="server" OnCommand="bntCancel_Command" ImageUrl="~/internal/images/cancel.gif" /> 
 <td></tr></table>

My Vb page code

Protected Sub btnAdd_Command(sender As Object, e As CommandEventArgs)
 ...

 End Sub

My jquery script

function addBoard() {
        $("#divModal").dialog();

    }

EDIT: When I click that btnAdd on my jquery dialog, then nothing happens.I put a breakpoint in my vb code but it is never hit. This is my question.