You should be able to use background-images with repeat-y in a left and right table cell.
If cell-spacing is 0 then there should be no space but if you have a positive size then there will be a space between the shadow and the center content so you need to set the cells with the background-image to 0 margin and padding:-
I've just tested this with shadow images for left and right sides 17px wide x 13px high and they repeat down the sides. Only the center cell had cellpadding for the text.
<table cellspacing="0" cellpadding="10" bgcolor="skyblue"><tr>
<td style="margin: 0; padding: 0; background:
url(images/main_left.jpg) repeat-y; width: 17px;"></td>
<td>
Main center content cell<br/>
Main center content cell<br/>
Main center content cell<br/>
Main center content cell
</td>
<td style="margin: 0; padding: 0; background:
url(images/main_right.jpg) repeat-y; width: 17px;"></td>
</tr></table>
or put the styles in classes in a stylesheet.
Code downloaded to my PC will be deleted in due course.
WIN7; IE9, Firefox, Opera, Chrome and Safari for Windows; screen resolution usually 1366*768.
Also IE6 on W98 with 800*600 and IE8 on Vista 1440*900.