get Order_Item_Id using magento api
===

I want to create invoice in to magento store using magento api in php.For that I want to create invoice for particular quantity and item means If anyone wants to invoice one item in paricular quantity then It shoud be done.My code is working for array() or all quantity.
Below is pseudo code for creating invoice 

    $client = new Zend_XmlRpc_Client('http://127.0.0.1:8080/AndroidMagento/api/xmlrpc')
    $session = $client->call('login', array('tester','tester'));
    $saleorderno = '100000007';
    
    Mage::init();
    $order = Mage::getModel('sales/order')->load($saleorderno);
    $orderItems = $order->getAllItems();
    $invoiceItems = array();


    foreach ($orderItems as $_eachItem) {
    $invoiceItems[$_eachItem->getItemId()] = $_eachItem->getQtyOrdered();
}

    $result = $client->call('call',array($session,'sales_order_invoice.create',array($saleorderno,array('order_item_id' => 9474, 'qty' => 1),'Invoice Created by Test',false,false)));

I have seen this [link][1] where i found somewhat idea but i can't understand exactly.I can't understand how to get **order_item_id**.  
Any idea??? Please suggest me Thanks in advance...
[1]:http://stackoverflow.com/questions/9678852/magento-sales-order-invoice-with-product-quantity-updation-using-api-not-working