Panel Closing on textbox text chnaged

I have a Panel on my vb.net web page. I used javascript to show and hide the panel. And there is one text box and Gridview within that panel. I want to load the grid on text change event of this text box. When this event fired, the Panel get closed. how can I prevent the panel close? AutoPostBack property of that textbox is true. I have given my code
Protected Sub txtSearch_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtSearch.TextChanged  
 If (txtSearch.Text.Trim() = "") Then       
  Else            
gvList.DataSource = ObjDataHandler.getByName(txtSearch.Text.Trim() + "%%")            
 gvList.DataBind()      
   End If  
  End Sub
...