Thanks for your response.I currently work on-site for Company A in Dallas,TX that is client of Compnay B (that sponsored my H-1B) which is also in Dallas,TX. Before working for Company B, I worked for Company C(based in Oregon), Company D (based in Maryland but I worked on-site for their client in New Jersey) and Company E also based in Dallas,TX.Also another issue for me is that the duties I am performing for Company B, only 50% of these duties will match what I did for my previous employers. That's why I am concerned that they might not agree to sign my experience letter which will eventually turn into Company B not processing my Greencard. That's the reason I am strssed, please help. Thanks a lot in advance!!!