Yes, you can. Once you finish your first 8 returns, you can select Tools>Licence Code Switch from the top menu to enter in your second code. 

Thanks for your answer.  I was not able to find answer for my question anywhere.

Just another quick question.   If the second code is entered in, will I still access to the previous 8 returns I did with the first code?  There won't be any issue opening any tax return again done with first and second code?

Thank you for your help again in advance.