Add new item automatically during delivery creation(tcode: VL01N)

Hi

Business requirement: Sales Order has material X. when delivery is created, system should add material Yautomatically in delivery.

Example:

Sales Order:

Item 10 Material X

Delivery:

Item 10 Material X

Item 20 Material Y

We are using 4.6C. We have tried to use Delivery Save Exits, but could not succeed.

Please provide inputs.

Regards

Uma