i am bcom graduate.please suggest me a course which can be completed within 2 to 3 yrs,which will give me 100% placement with a average pay

As a B.Com graduate, best option for you is to pursue MBA as regular candidate through CAT/MAT/CMAT in a good B-school. There if you perform well then during campus placement, you will get reasonable jobs.

NOT ONLY GO FOR MBA BETTER GO FOR CA,CFA,COMPANY SECRETARIATE,PROBATIONARY OFFICER OTHER RELATED COURSES AS OF NOW MBA HAS BECOME MOST ABUSED QUALIFICATION IN THE JOB ARENA AS COLLEGES WITHOUT PROPER INFRASTRUCTURE ALSO OPENS THE COURSE.