count doesnt get incremented

Hi,
  Here's my template which is not incrementing the
count value whenever <mo>(</mo> is matched in the
document.
 
<xsl:template match ="mml:mo[.='(']">
<xsl:variable name ="moWithParen"
select="count(preceding::mo[text()='('])"/>
<xsl:text>&lt;form name = "</xsl:text><xsl:value-of
select ="$moWithParen"/><xsl:text>"&gt;</xsl:text>
</xsl:template>


Always the output is  <form name ="0"> it is not
getting incremented.

kindly help is appreciated

Thank you
suresh 

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