Joomla CSS: Copy some container elements to another section

[subster]

Hi there,

i really enjoy this beautiful Board, perhaps you can help me, i would really appreciate that ;)

My Menudesign on my joomla Installation is defined like that:

div#menu .menu-m {
height: 43px;
padding: 15px 0px 0px 0px;
background: url(../images/menu_m.png) 0 0 repeat-x;
}

div#menu .menu-l {
position: absolute;
top: 0px;
left: 0px;
width: 20px;
height: 58px;
background: url(../images/menu_l.png) 0 0 no-repeat;
}

div#menu .menu-r {
position: absolute;
top: 0px;
right: 0px;
width: 20px;
height: 58px;
background: url(../images/menu_r.png) 0 0 no-repeat;

Now i want that around the content-section, which is defined with this:
.contentpaneopen {
border: 1px solid #000; }

My Question is: How can i implement the 3 Elements of the menu (the three border-grafics) into the .contentpaneopen - element?

Thank you very very much for help, i had much sleepless nights on this issue but cant solve it.