Assigning variable values

Could somebody help me on this issue? I am having a
problem assingning values to a variable. Look 
the example:

--------------------------------------------
These ones were declared globally:

<xsl:variable name="teste" select="'um'"/>
<xsl:variable name="um" select="'um'"/>
<xsl:variable name="dois" select="'dois'"/>
--------------------------------------------


--------------------------------------------
This code was declared inside a template:

<xsl:choose>

       <xsl:when test="$teste = 'um'">
            <xsl:variable name="teste"><xsl:value-of 
select="$dois"/></xsl:variable>
       </xsl:when>

       <xsl:otherwise>
            <xsl:variable name="teste" select="$um"/>
       </xsl:otherwise>

</xsl:choose>

<font face="arial" size="3"><xsl:value-of
select="$teste"/></font>
--------------------------------------------


This code only returns me the value 'um'. The when
clause is working, 
but the assigning of value to the $teste variable is
no working 
inside the choose clause.

Could somebody please help me? Thank you very much!

Georges Claessen
Brazil

__________________________________________________
Do You Yahoo!?
LAUNCH - Your Yahoo! Music Experience
http://launch.yahoo.com

 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list