hi,

see it seems not clear the real query of questions. if you want to change the shift in same college where currently  you have taken admission in b.com (//b.com) morning session, then you have to make contact with college authority to change your shift timing and it would also depends on the availability of seat in that particular batch. however if you want to take fresh admission to b.com (//b.com) evening classes look for colleges website if still admission is going on or not.