3 column liquid header, with fixed image for center...

hello, wondering if anyone can help - i currently have 3 columns for my header:

.h-left{
background:url('img_rep.gif') repeat-x;
height:165px;
float:left;
width:24%;
border-right:1px solid #0041B1;
}
.h-right{
background:url('img_rep.gif') repeat-x;
height:165px;
float:left;
width:24%;
border-left:1px solid #0041B1;
}
.h-middle{
background:url('img_rep.gif') repeat-x;
height:165px;
float:left;
width:48%;
}

This works great, but now i want to have the middle column displaying an image (width:895px), but im not sure what I can put for the width in the left and right columns to get it to display accross the page, depending on the size of the middle image...(i.e. so it automatically adjusts depending on the size of the middle column + screen size)

any help would be appreciated, cheers.