How to do leap frog - L1B to H1B

[devex]

I am currently on L1B Visa with Company A. Company B applied for my H1B in October 2011 which i don't know was with a Change of Status request or not. I haven't got the H1B approval yet, its still in process with USCIS and I assume it was with a Change of Status request but i don't know what is my Change of Status Start Date. I want to continue working on L1 with Company A upto 2012 year end because of some personal reasons. I want to do "Leap frog" in order to maintain my status on L1B but as i don't know what is my Change of Status start date or may be the change of status is prior to the H1B approval date (which i haven't got yet as i mentioned above).
So my questions in this regard are as follows:
1. Please suggest me how can go for Leap frog when i don't know what is my change of status start date.
2. How can do leap frog if my change of status start date is prior to my H1B approval date which is not approved yet and is in processing with USCIS?

Thanks in advance!

[devex]

Can anyone please reply as this urgent?
I would appreciate your valuable inputs!

[kabkaba]

Once B receives approval, you will have to leave the US and return using your L1 Visa and petition. That will take care of your status. However, note that there is a gap of few days between the day of H1 approval and the day you leave the US. You will be out of status during this gap. So it is good to leave the US as soon as you hear about the H1 approval. Ask B if they had filed as change of status and ask them for receipt number to track online. If filed with COS, then leave the US as soon as online status changes to approved.