Is there a way of finding out if a block will have content from a template?

For example, I might have a theme that has an absolute div for a right
block.
If the right block does not have content I dont want to display the div so
as to avoid an empty column.

I have been able to do this by assigning the content to a variable and then
working on if the variable is empty.
eg. in default.xt:

<xar:set name="$foo"><xar:blockgroup name="right" id="right" /></xar:set>
<xar:if condition="$foo ne ''">
<div class="blockright" id="blockright">
#$foo#
</div>
</xar:if>

- Apparently this kind of issue will be handled when BL is changed to xslt.