My dear friend,
As you said that you have completed your graduation in B.Com and now you want to go for higher studies but my friend let me tell you that B.Arch is not considered as the higher studies because it is also the graduation course so why are you crazy about it.
If you want to make your career then please select at least one field and make yourself perfect in it rather than go to one and then another.It is not the way to fulfill you aim.So my friend please make sure that your interest in which field.
Then according to your interest you have to put your step further.And my friend MBA is the post graduation course for which you can go.I am not saying that you can not go for B.Arch,you can go but the thing is that you waste your time to do 2 graduation course because for the admission in B.Arch you must have completed your 12th with more than 50% with in non-medical stream.
And if you have completed your 12th with commerce then you can not go for B.Arch after B.Com.The only choice is MBA so you can go for MBA and chose the stream in MBA according to your field in graduation.
There are various streams in MBA i.e.post graduation course in business administrator.So be sure for the selection of the course and according to your choice and interest select the appropriate course.