Hi you can do this using magento event and observe and on create an event on catalog_product_save_after and check on obsever child product are out stock an set configurable accoring to ite
<global> <events> <catalog_product_save_after> <observers> <stockalert> <type>singleton</type> <class>check/observer</class> <method>autoupdatemy</method> </stockalert> </observers> </catalog_product_save_after> </events> </global> and observer.php
public function autoupdatemy($observer) { try{ $isstcok=false; if($observer->getEvent()->getProduct()->getData('type_id')=='configurable'){ $ConfiProduct=$observer->getEvent()->getProduct(); $allProducts = $ConfiProduct->getTypeInstance(true) ->getUsedProducts(null, $ConfiProduct); foreach ($allProducts as $product) { if($product->getIsInStock()==1): $isstcok=true; endif; } $stockItem = Mage::getModel('cataloginventory/stock_item')->loadByProduct($ConfiProduct); if($isstcok=true): $stockItem->setData('is_in_stock', 1); else: $stockItem->setData('is_in_stock', 0); endif; $stockItem->save(); } }catch(Excpetion $e){ Mage::log(print_r($e->getMessage(),1),'null','mage32173.log'); } return;}