Filling an MVC dropdown based on selections from a textbox (datepicker) .NET/Jquery/JS/MVC

I have the following 2 textboxes and dropdown

   <div class="form-group">
                @Html.LabelFor(model => model.StartDate, htmlAttributes: new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @Html.EditorFor(model => model.StartDate, new { htmlAttributes = new { @class = "form-control datepicker", @id = "StartDate", required = "required" } })
                    @Html.ValidationMessageFor(model => model.StartDate, "", new { @class = "text-danger" })
                </div>
            </div>

            <div class="form-group">
                @Html.LabelFor(model => model.EndDate, htmlAttributes: new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @Html.EditorFor(model => model.EndDate, new { htmlAttributes = new { @class = "form-control datepicker", @id = "EndDate", required = "required" } })
                    @Html.ValidationMessageFor(model => model.EndDate, "", new { @class = "text-danger" })
                </div>
            </div>
            <div class="form-group">
                @Html.LabelFor(model => model.Hours, htmlAttributes: new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @Html.DropDownListFor(model => model.Hours, (SelectList)ViewBag.hoursddl, "", htmlAttributes: new { @class = "form-control", required = "required" })
                    @Html.ValidationMessageFor(model => model.Hours, "", new { @class = "text-danger" })
                </div>
            </div>

I need to populate the dropdown based on the DateDiff multiplied by 8. Or I guess DateDiff + 1 * 8 minus 1 until it hits 1.
So if 3/1/2016 and 3/4/2016 are selected in the textboxes respectively, the dropdown would fill with 32, 31, 30, 29, 28, 27, 26, 25, 24, and so on until it reaches 1.

Any ideas?