Action returning Partial view and model

Action returning Partial view and model

I'm new to MVC 3 and I have a question regarding the correct approach.
Imagine I have a form
<tr>
<td class="editor-field">
 @Html.TextBoxFor(m => m.UserName)
</td>
</tr>
....
And model:
   [Required]
    public string UserName { get; set; }

    [Required]
    public DateTime? Birthdate { get; set; }
    ....
And somewhere in middle I have a:
@Html.Action("LocationGroup", "Home")
Which will load a new partial view with group of controls together:
    [ChildActionOnly]
    public ActionResult LocationGroup()
    {
        Model model = new Model();
        return PartialView("_TempView", model);
    }
Basically my question is, how can i merge this model together with data, i mean in that LocationGroup method, I have to create a new model, I can't pass existing.
With other words I'm kinda lost with the Models in this particular situation.
Cuz also after submitting the form, how can i retrieve the data, from that partial view with action?
Any help is appreciated