Button that prevents multiple clicks

private void BuildClickOnceButton(WebControl ctl)
{      
    System.Text.StringBuilder sbValid = new System.Text.StringBuilder();
    sbValid.Append("if (typeof(Page_ClientValidate) == 'function') { ");
    sbValid.Append("if (Page_ClientValidate() == false) { return false; }} ");
    sbValid.Append(ctl.ClientID + ".value = 'Please wait...';");
    sbValid.Append(ctl.ClientID + ".disabled = true;");
    //GetPostBackEventReference obtains a reference to a client-side script function that causes
    //the server to post back to the page.
    sbValid.Append(ClientScript.GetPostBackEventReference(ctl, ""));
    sbValid.Append(";");
    ctl.Attributes.Add("onclick", sbValid.ToString());
}