yes, you can easily pursue MBA in marketing and that can be done through an executive course or a regular one. for the regular one, you need to leave your job and join an institute and for the executive one, it depends on the institute. You need to take CAT/XAT/NMAT/SNAP/MAT/CMAT to get admission in the top b-schools of the country. And choosing a stream in MBA doesn't go sync with the work ex. You can go for MArketing, finance or HR.