[xsl] Select nodes with an attribute but not all the nodes

[<mysrdr-wrk@xxxxxxxxx>]

I am making an XML to XML transform using XSLT 2.0 and
Saxon 8B.  I need to select certain nodes based on an
attribute, but when I find a node without the
attribute I want to stop selecting nodes even if
subsequent siblings have the attribute.  
   
  <level2>
              <name>box</name>
              <number>1234</number>
  </level2>
  <level2>
              <name attachpart=1>washer</name>
              <number>234</number>
  </level2>
  <level2>
              <name attachpart=1>screw</name>
              <number>345</number>
  </level2>
  <level2>
              <name attachpart=1>bolt</name>
              <number>456</number>
  </level2>
  <level2>
              <name>nameplate</name>
              <number>9876</number>
  </level2>
  <level2>
              <name>switch</name>
              <number>7654</number>
  </level2>
  <level2>
              <name attachpart=1>screw</name>
              <number>345</number>
  </level2>
   
  The washer screw and bold are attaching parts for
the box. I need to output these in an <attachingPart>
element.  
   
  <record>
              <name>box</name>
              <attachingPart>234 345
456</attachingPart>
  </record>
   
  Depending on how I approach the code, I get nothing
or just the washer or I get *all* of the parts that
have the attachpart attribute.  Is there some way to
say stop selecting attachpart nodes when a level2
doesnt have the attribute?  Its sounds so simple but
Im not getting anywhere with it. 
 
I've been reading both Michael and Jeni and checking
the archives.  Some things look close but I get the
same results. The answer is probably right in front of
my face but Ive been looking at it so long I cant
see the forest for the trees.
   
  Regards,
  Hermy