format % issue

Hi

What is the workaround to just print the % number ?

Fatal Error! Required item type of first argument of format-number()
is numeric; supplied value has item type xs:string


	<xsl:template name="display-percent">
		<xsl:param name="value" />
		< xsl:value-of select="format-number($value,'0.00%')" />
	</xsl:template>


<xsl:if test="$testcase=1">
	<xsl:call-template name="display-percent">
		<xsl:with-param name="value" select="$successPercent" />
	</xsl:call-template>
</xsl:if>
<xsl:if test="$testcase=3">
	<xsl:call-template name="display-percent">
		<xsl:with-param name="value" select="$successPercent" />
	</xsl:call-template>
</xsl:if >