Transfer 485 to another 140

[closeby]

I have EB-2 140 approvied in 2006 with PD 8/29/05. I filed EB-1 140 and 485 in March 2007 and its 140 is still pending. My attorney is suggesting to transfer the Eb-1b 485 to the EB2 140. I heard from some discussion that both 140 must be approved before we can do the transfer. Can anyone please answer the question and kindly indicate where to find the official document concerning this issue? Thanks a million!