node form submit alter values of field in inline entity reference.

Hi Thank you for this module.

Im using it as part of the commerce kickstart distribution

On my product variation type I have a few fields which i am trying to modify upon submission of the node creation form.

When I inspect the fields I get structures such as

field_product['und'][0]['form']['new_reference_field']['und'][0]['target_id']

But If I try code such as

node_presave($node){
$node->field_product['und'][0]['form']['new_reference_field']['und'][0]['target_id'] = 1;
}

nothing happens

What do I need to do to modify the values of the IEF?

Thank you for any help