Pop up bbdb right of article buffer

[Tassilo Horn]

Hi,

I use Gnus with bbdb and when I open a mail whose sender is in my bbdb a
new window pops up below the article buffer like this:

+-----------------------------------------------------------------+
|                                                                 |
|                                                                 |
|                Summary Buffer                                   |
|                                                                 |
|                                                                 |
|                                                                 |
+-----------------------------------------------------------------+
|                                                                 |
|                                                                 |
|                                                                 |
|                                                                 |
|                                                                 |
|                Article Buffer                                   |
|                                                                 |
|                                                                 |
|                                                                 |
|                                                                 |
|                                                                 |
+-----------------------------------------------------------------+
|                                                                 |
|               BBDB Buffer                                       |
|                                                                 |
+-----------------------------------------------------------------+
                           
What I want is that the bbdb buffer pops up right of the article buffer
like here:

+----------------------------------------------------------------+
|                                                                |
|                                                                |
|             Summary Buffer                                     |
|                                                                |
|                                                                |
|                                                                |
+-----------------------------------------+----------------------+
|                                         |                      |
|                                         |                      |
|                                         |                      |
|                                         |                      |
|                                         |                      |
|                                         |                      |
|             Article Buffer              |     BBDB Buffer      |
|                                         |                      |
|                                         |                      |
|                                         |                      |
|                                         |                      |
|                                         |                      | 
|                                         |                      | 
+-----------------------------------------+----------------------+ 

The article buffer should at least be 90 columns wide, the rest should
be for bbdb. One thing which prevents me from using
gnus-add-configuration is that the bbdb buffer should only be there when
the article's sender is in my bbdb. If not the bbdb buffer should be
closed.

All in all: How can I change the bbdb popup window's position without
changing the default bbdb behaviour?

If there are some variables/functions to do this, pointing me to them
should be enough, I hope.

Much thanks in advance, 
Tassilo