counting nodes before and aften an specific one

Hi xsl people.

xml sample
<form-tab>
  <tab active="0" name="GENERAL"/>
  <tab active="0" name="CONTABLES"/>
  <tab active="1" name="NOTAS"/>
  <tab active="0" name="DOCUMENTOS"/>
  <tab active="0" name="NOTAS"/>
  <tab active="0" name="RELACIONES"/>
</form-tab>

how can I count the nodes before the one @active=1
ant the ones after, assuming there is only one active

any idea?

thanks in advance
Ani

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