Can i file a lawsuit against the company I am currently employed with for breach of verbal contract and loss of potential pay?

In September 2008, my supervisor promised me a promotion on the terms of me being able to obtain my LASAC (license in substance abuse counseling. I work for a non-profit behavioral health agency). I passed the licensure test and submitted my application for the LASAC. My company hired a new employee specifically for my position whom I was instructed to train for my position, as this individual would be taking over for me when I completed the transition to the promoted position. I trained this individual for my position for 2 solid months with her "shadowing" me on a daily basis. By the end of those 2 months, this individual had mastered my position. My promotion was not known to just me, but to my colleagues, including those I would be supervising in the future, and my clients (everyone at my company was verbally informed by the supervisor that promised me the promotion, not me. I told no one). Unfortunately, an issue arose where I was not able to get my license (I did not meet the requirements in getting a license). As a result, I was not able to be promoted, which I understood. With my ambitions, I had asked my supervisor if there was anything I could do to still be able to secure the promotion and she repeatedly told me no. Last I heard, the company was interviewing applicants with licenses. Last week, I was non-chalantly informed that my company decided to change the qualifications needed for that promotion so that a license was NO LONGER required, thus making me more than qualified to be promoted. The company interviewed another applicant, who had if not similar, but less qualifications than me (she had less experience in only one setting, whereas I have experience in 5 different settings in the company, has been with the company for less amount of time, has no license, and has less education). I am the highest producer in my company and have been for the last 6 months. My work is known not just by fellow counselors but by the prescribers as well. Even though I had repeatedly asked my supervisor if there was anything else I could do to secure the promotion, she continued to tell me no, and deliberately did not tell me that the company had changed the qualifications needed for that promotion thus making me eligible. I was denied any opportunity to fight for the promotion that was promised to me and rightfully mine. This is the second time a position was promised to me only to have that position given to that same woman. I had addressed my concerns with the HR director who adverted all my questions, repeatedly only saying, "we do what is in the best interest of the company". I have a strong suspicion that my company decided not to promote me because by doing so, there would be a substantial loss in company profit, as the promotion would put me a position where I would not be able to bill for the amount of services I currently provide. Not only am I baffled by the promotion, but my colleagues, including my replacement and those I would be supervising, are as well. Nonetheless, I am dealing with breach of verbal contract and loss of potential pay. My problem is this : although I have more than several witnesses who were aware of my promotion and who are all willing to testify if needed, there was nothing in writing. Regardless, I want to pursue legal action.