I'm trying to set the value of a custom field on an order when saving an entry. I found [an example of how to do this][1] for a simple text field, but the field I'm trying to set is an **entries** field, not just a text field. I've attempted to set the value using the following code in my entries.saveEntry event. I'm assuming I'm doing this wrong since this is an entries field, not a simple text field, but I don't know the syntax for setting content on an entries field.

    $cart = craft()->commerce_cart->getCart();
    $cart->setContentFromPost(['entriesFieldHandle' => $entry->id]);


  [1]: https://craftcms.stackexchange.com/questions/15165/how-can-i-update-a-custom-order-field-in-a-plugin-controller