Help Needed!! H1B Transfer..Important

  1. I currently work for a company fulltime Company “A”. I have visa stamped till Sep 2015.

  2. I am traveling to Canada this July end - 7-8 Days

  3. I just got an offer from Big company “B”. I would like to join the company in Aug first week and would not like to leave company A before my canada trip

Now my question is Company B is going to do my H1B transfer in Premium processing ( which takes 2 weeks)

A . If I am in canada and the transfer is successful will there be a problem with me entering US , as I would be still working for company A? ( will my Current Employer A know?) - I know that I need not get my visa stamped atleast until my visa expiry