How to show control over another?

Question

Hi! I have a problem, I'd like to write some control (like ComboBox), but in context menu I need to upload some control... So, how could I show my control (my context) over the parent form (over Grids, etc)?..

I need smth. like this:

---------------------------------------------------
my control->my control -> my control
---------------------------------------------------
                       |                 |
                       |                 |
                       |my context|
  PARENT         |                 |   FORM
 With it own's  |                 |   Grid's
                       |                 |   and etc...
                       |_________|