XSLT - update attribute with new value

Many thanks to everyone who offered help with my stylesheet. Everyone's
suggestions worked when using a hardcoded value for the attribute name. 
But I need to use parameters.

this is what I've tried so far.  Is there another way?

thanks,


Ann Marie

<xsl:param name="attr">ROSE</xsl:param>
<xsl:param name="value">RED</xsl:param>
<xsl:param name="node">orion-web-app</xsl:param>

 <xsl:template match="orion-web-app"> 
 <!-- adds attr to orion-web-app node correctly but won't
    take vars for attr or match="$node" -->

    <xsl:copy>
         <xsl:if test="not(//@ROSE)">
               <xsl:attribute name="ROSE"><xsl:value-of
select="$value"/></xsl:attribute>
               <xsl:apply-templates select="@*|node()"/>
         </xsl:if>  
    </xsl:copy> 
 
     </xsl:template>
 
If i include the attr test in this template:

 <xsl:template match="@*" priority="10">
 <!--   adds attr to each node in the tree
         it should only be added to the specified node
         and vars are not allowed where ROSE is used -->

         <xsl:if test="not(//@ROSE)">
           <xsl:attribute name="ROSE"><xsl:value-of
select="$value"/></xsl:attribute>
         </xsl:if>-->  


to get around the restriction on where attribute names can be used, I
tried this:

<xsl:template match="@*" priority="10">
       <!--replaces every attr in the result tree w/ RED
        recoverable error: Cannot write an attribute node when no
        element start tag is open-->
     
        <xsl:choose>
        <xsl:when test="not(//@*=$attr)"><xsl:value-of
select="$value"/></xsl:when>
        <xsl:otherwise><xsl:value-of select="."/></xsl:otherwise>
        </xsl:choose>