Loading/Please-Wait Pop-Up in MVC View

I have developed a web application using MVC architecture. My controller takes some time to process input, send it to the server and return it back to the view. I want a Loading/Please-wait kind of pop-up to be shown and exited automatically when the ActionResult returns the view. The corresponding part in my controller looks like this:

[HttpPost][STAThread]
    public ActionResult Index(DropDownModel model)
    {

        BillingToolInterface_1.Program p = new BillingToolInterface_1.Program(state, billtype, recurring, budget, paytype, IA, spanish, veteran, status, LDC, rate, adjustments, billtemplate, readtype, server1, server2, choice, paramcheck);

         //above step takes like 15 seconds to put the server result in       
//DataJoin.Connector.data. I want a dialog to be displayed during this time. 




        model.Message = DataJoin.Connector.data; 


        return View(model);
    }

You can use something like this to submit your form:

@using (Ajax.BeginForm("Index", "Controller", null, new AjaxOptions {HttpMethod = "POST", LoadingElementId = "please-wait"}, new {-- some html if needed --}))

That will show the please wait message until the callback finishes. The please-wait could be some markup like:

<div id="please-wait" style="display: none;">
    <div class="modal"></div>
    <div class="spinner">Loading...</div>
</div>

The css for that markup could be (not the best css but works):

#please-wait
{
    position: absolute;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
}

    #please-wait .modal
    {
        z-index: 1999;
        left: 0;
        top: 0;
        width: 100%;
        height: 100%;
        opacity: 0.5;
        -moz-opacity: 0.5;
        background-color: black;
        margin-left: 0;
    }

    #please-wait .spinner
    {
        z-index: 2000;
        padding-top: 20px;
        padding-left: 20px;
        background: #E5E5E5 url("loading.gif") no-repeat 15px center;
        width: 120px;
        height: 40px;
        border: 2px solid #666;
        font-weight: bold;
        text-align: center;
        position: relative;
        margin-left: auto;
        margin-right: auto;
        top: 35%;
        display: block;
    }