using grid in update panel

i have above code

but the  div.Visible = true;     textbox1.Visible = true; are not visible

secondaly the b1 click event happens only once

if i again click the script does not get executed

function MouseUp(e)
{
document.getElementById('b1').click();
}


  protected void btnpb_Click(object sender, EventArgs e)
      {

        try
        {


    div.Visible = true;
    textbox1.Visible = true;
}
}


<asp:UpdatePanel ID="Panel1" runat="server">

      <ContentTemplate>

  <asp:GridView ID="grid1" runat="server" >

 

  </asp:GridView>

  <Triggers>
    <asp:AsyncPostBackTrigger ControlID="b1" EventName="Click" />
  </Triggers>
  </asp:UpdatePanel>
  <br />
   
  <asp:Button ID="b1" runat="server" Text="" />