When to apply for H4 Change of Status for L2 Dependant



Currently i am on L1 B and i have applied for H1 thru company B.  I have got  RFE on 7/23 and my employer B has answered the RFE and i am waiting for decision to be made by USCIS. My Situation here  is: I can get my approval anytime and because its going come after October 1st. I think it will come as Active and my wife's L2 will become inactive. So, when do i have to apply for my wife's H4 COS. Can i apply now with the copy of my H1 Receipt or i have to wait till i get the approval. My wife has a valid I-94 till Jan 21st 2013.


Please help me with this issue and let me know the list of document required to apply of H4 Change of Status.