Execute addon code before block

Hello



I've created an addon which includes a static template block.

My question is, how can I execute code before the static block is rendered?



Static block path:

design/themes//templates/addons//blocks/static_templates/filter.tpl



Addon structure so far:

app/addons//addon.xml

app/addons//func.php

app/addons//init.php



Regards