BBA and CA are two different courses. As CA is a self study program you can do a BBA program along with your CA. However, as CA is a very tough program and would need a lot of focus and hard work so, you should plan both CA and BBA only if you feel that you can do justice to both the programs.

Moreover, since you have not mentioned from where you'll be pursuing your BBA, hence i cannot  tell you how much time you'll be able to devote to both the courses partially. It gets difficult especially for students who do BBA from regular college and the college has minimum attendance criteria because then it's really difficult for students to take out time for their coaching and self study. However, I'll recommend you to opt for both the courses together or go for direct entry scheme in third year of your college.

Hope this helps.

Good luck