newbie variable question

I'm an XSLT newbie.  I've been trying to get this one thing to work for
a while now and I just can't get it to work.  I'd apreciate any help
that anyone can provide:

What I am trying to do is:
if there are any grp/type element whose contents are "DMA" I want to
print out the value of the associated name in that grp.  if there is no
grp/type element whose contents is "DMA" I want to print out the values
of the description element.

my XML that looks like this:

     <area>
       <grp>
         <type>MSA</type>
         <name>foo</type>
       </grp>
       <grp>
         <type>DMA</type>
         <name>bar</type>
       </grp>
     </area>
     <description>baz</description>

and the XSLT I'm working with looks like this

  <xsl:for-each select="area/grp">
    <xsl:if test="string(type)='DMA'">
      <xsl:value-of select="name"/>
     <xsl:variable name="ValueExists" select="'True'"/>
    </xsl:if>
  </xsl:for-each>
<xsl:if  test="$ValueExists!="'True'">
 <xsl:value-of select="description" />
</xsl:if>


but I keep getting an error:

A reference to variable or parameter 'ValueExists' cannot be resolved.
The variable or parameter may not be defined, or it may not be in scope.

I'm using the MS XSLT translator.  Thanks for any help you can provide,

Les


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