The INS has still not issued any regulations under AC21 yet!
The following posting is from the
http://www.murthy.com/UDac21qa.html web page.
"AC21 Frequently Asked Questions
"We at The Law Office of Sheela Murthy receive many questions about the portability provisions of The American Competitiveness in the Twenty-first Century Act (AC21) for Adjustment of Status applicants. These questions arise daily in consultations with our clients and on the MurthyForum, as well as in our weekly MurthyChat. What follows are Frequently Asked Questions and their answers under the actual law with INS\' present interpretation. It is important to keep in mind that INS is not bound by their present interpretation and position, although it is likely that, when finally issued, their regulations will be consistent with these earlier interpretations. To provide some comfort and support, Mr. William R. Yates, Executive Associate Commissioner at INS Headquarters, Washington, D.C., has advised us at various meetings that a good-faith and reasonable interpretation of the AC21 should not and will not subject one to penalties for violations of the law.
"Essentially, AC21 allows for approval of employment-based adjustment of status applications through an employment offer other than the one contained in the labor certification and I-140, provided certain requirements are met. Those eligibility requirements under section 106(c) of AC21 are that (a) the I-485, Application for Adjustment of Status, must be pending (unadjudicated) for 180 days or more; and (b) the new job must be the same as, or similar to, the job described in the labor certification and I-140 petition. As of this March 2002 writing (and as regular MurthyBulletin and MurthyDotCom readers are aware), the INS has still not issued any regulations under AC21.Therefore, much uncertainty still remains with respect to many matters."
There is also a couple of answers to FAQs on that same webpage.
Hope this will give you an idea.
Thanks and good luck to you.