Hi Ram,
The Transaction I mentioned is indeed in SAP ECC (not in GTS), so it should meet your requirement. Basically it's a way to produce a Billing Document for all items in a Shipment, which I think is what you are wanting.
Whoever is responsible in your organisation for creating and submitting Export Declarations should be authorised to create Billing Documents (only) for transfer to GTS from each relevant Shipment so that the corresponding Declarations can be created and processed.
Let us know if you need any further information.
Regards,
Dave