Transfer of H1 in 6th.year when labor in process - Urgent

[ks_fl]

Hi,
I am working for Company "A", which has applied for my Labor through PERM which is still pending. I am in the 6th. year of my H1B visa. Now I want to transfer to company "B". I understand that Labor cannot be transferred but here are my questions,
1). Can I transfer my H1B to Company "B".
2). If I can transfer my H1 to Company "B", I will be starting a new Labor petition process with the company "B" (please note that I am already in the 6th. year). Then, can I use the Priority Date of my Labor petition filed through company "A" to get 7th., 8th. year extensions etc. with Company "B". Do I have to have Company "A"'s blessing to do this? I do'nt want any influence of Company "A", is this possible? Can Company "A" do anything at all?

I have some vague idea how it works. Company A applies for seventh year extension and Company B first applies for Labor and then does H1B transfer based on the seventh year extension of Company A. May be this way the old Priority Date (Labor application from Company A) may be maintained.

Can anyone please give the detail picture more clearly?

Many thanks in advance.

[ks_fl]

Is there any way to maintain the PD from Company A even if I join Company B?

This is very urgent ... Please help.

Thanks a lot.