in view page, HttpPost is firing only for the first time on pressing TAB Button in TextBox in mvc 4 c#

1. I have 4 text boxes and one button in my view page in asp.net
    with c# and MVC.

2. now, on pressing TAB key in first text box, I am calling Stored procedure from a controller and getting Value from one table and displaying that value in second text box..

3. I am doing it using Java script or jquery ...using <http post>..
But Http Post is going to controller only when the page is loaded for the first time....

4. If i Press TAB key for the second time , the page is not posting and Http Post is not firing.

Please Help....Thanks in advance

@model Mvc4App10.Models.Loan_Account
@{
    ViewBag.Title = "Register_Loan_Account";
}
@{
    var message = TempData["AlertMessage"] ?? string.Empty;
}

<script src="../../Scripts/jquery-1.7.1.min.js" type="text/javascript"></script>
<script src="../../Scripts/jquery.unobtrusive-ajax.min.js" type="text/javascript"></script>
<script type="text/javascript">

    $(document).ready(function () {
        $('#EMPID').change(function () {
            $.ajaxSetup({
                // Disable caching of AJAX responses
                cache: false;
            });
            $('form').submit();
        });
    });
    </script>

<h2>Register_Loan_Account</h2>

@using (Html.BeginForm())
{ 
  @Html.ValidationSummary(true)

    <fieldset>
       <div class="Editor-label">
         @Html.LabelFor(model=>model.EMPID)
       </div>
       <div class="Editor-field">
        <p> @Html.TextBoxFor(model => model.EMPID, ViewBag.FilterValue as string)</p>
<--clicking Tab key...values from other table is taken using stored procedure from controller and that value is displayed in textbox 'LAmount' -->
         @Html.ValidationMessageFor(model=>model.EMPID)
       </div>

       <div class="Editor-label">
         @Html.LabelFor(model=>model.Rate)
       </div>
       <div class="Editor-field">
         @Html.TextBoxFor(model => model.Rate, ViewBag.FilterValue as string)
         @Html.ValidationMessageFor(model=>model.Rate)
       </div>   

       <div class="Editor-label">
         @Html.LabelFor(model=>model.LAmount)
       </div>
       <div class="Editor-field">
         @*@Html.TextBoxFor(model => model.LAmount, ViewBag.FilterValue as string, new { Value = ViewData["Empid"] })*@
         @Html.TextBoxFor(model => model.LAmount, ViewBag.FilterValue as string)
         @Html.ValidationMessageFor(model => model.LAmount)
       </div>

       <div class="Editor-label">
         @Html.LabelFor(model=>model.Balance)
       </div>
       <div class="Editor-field">
         @Html.TextBoxFor(model => model.Balance, ViewBag.FilterValue as string)
         @Html.ValidationMessageFor(model=>model.Balance)
       </div>

       <div class="Editor-label">
         @Html.LabelFor(model=>model.Remarks)
       </div>
       <div class="Editor-field">
         @Html.TextBoxFor(model => model.Remarks, ViewBag.FilterValue as string)
         @Html.ValidationMessageFor(model=>model.Remarks)
       </div>
      
       <p>
         <input type="submit" value="Register" />
       </p>
    </fieldset>
    
    <div>
       @Html.ActionLink("Back to Index","IndexManualGrid")
    </div>
    
}

[HttpPost]
        public ActionResult Register_Loan_Account(Loan_Account Loan1)
        {
             //code....everything is working fine when the page is loaded for the first time....its calling jquery only for the first time...but after then its not coming to controller...plz help
        }