Under C. Excise law there is no prohibition on bringing duty paid goods inside the factory. Prior to 2001, this was prohibited/regulation under rules 51A and 173H.
But you must bear in mind that department would tempt to be uncomfortable with the arrangement because the activity as it is prone to misuse. Therefore, take such precaution that nobody can ever allege that the traded goods were manufactured in your factory and was removed without paying duty. I suggest following steps:
i. Inform your Range Supdt. before commencing the activity. Give him broad descripttion of the goods; say that you will not work under rule 16 of C. Excise Rules; that you clear goods under delivery challans and commercial invoices; and that you shall maintain record of receipt, issue and stock of the goods.
ii. Maintain physical separation between goods manufactured in your factory and the duty paid stock received for trading.
iii. Maintain proof that the goods have been received from outside (challans, invoices, transport documents, etc.)
iv. Maintain a stock register for such goods.