Rearrange childes of VBOX

[AlannY <m alanny ru>]

Hi there ;-)

I have a window with included vbox, which includes some count of 
widgets. When I press button, I want to change position of this widgets 
in this vbox ;-) How to do it?

ANSI art:

+------------------------------------+
| Window                             |
|  +------------------------------+  |
|  | vbox                         |  |
|  |  +------------------------+  |  |
|  |  | widget 1               |  |  |
|  |  +------------------------+  |  |
|  |  +------------------------+  |  |
|  |  | widget 2               |  |  |
|  |  +------------------------+  |  |
|  |  +------------------------+  |  |
|  |  | widget 3               |  |  |
|  |  +------------------------+  |  |
|  |  +------------------------+  |  |
|  |  | widget 4               |  |  |
|  |  +------------------------+  |  |
|  +------------------------------+  |
+------------------------------------+

I want to switch position of widget 1 and (for example) widget 4. How to 
do it?

P.S. Also I want to do it with DnD, but, for now, it's not so important ;-)