H1-b 8 th yr extension with pending perm

[shur]

Hi ,

Below is my case

Worked for Company A with H1- validity till Oct -2010 . Perm was applied in Apr 2008 ..went into Audit. Based on pending perm I got H1 extension till Oct -2011. My Perm was denied after Audit. Changed to company B and got my h1-b under new company B till Mar -2012. Now my perm has been filed by company B in Jan 2012. I understand I will need to leave the country before MAr 2012 . When can I re-enter the country if all goes well? I need to have my perm approved and I-140 approved and then i can apply for my H1-b extension ? Also when my GC is in process and I am out of the country can I continue to be on US payroll i.e from the period of MAr 2012 to the time my I-140 is approved?