defining nodes to apply template to

<root>
        <item>
                <blah>TEXT</blah>
                <blah>TEXT</blah>
                <blah>TEXT</blah>
                <blah>STOP</blah>
                <blah>TEXT</blah>
                <blah>TEXT</blah>
        </item>
</root>
i want to apply a template to all <blah> nodes before
the text STOP appears after that I do not want to
apply the template in the <blah> node.
i believe the rough answer is to do with XPATH and
setting the template match correctly using
preceding-sibling
but can't quite work it out...
any help appreciated.