I have a certain type of certification that is a hard requirement for about 25% of the work I do. I believe this was a strong factor in the decision to hire me. There is a possibility I may lose this certification in the near future, but I would like to continue working for my current company.
I have a meeting with my manager next week. I will explain the situation, say that I have an offer from a different company, but I would prefer to keep working here if I had some assurance that they wouldn't fire me if I lose this certification.
My question is: what sort of assurance should I ask for? Would a written document signed by the manager be enough to cover me? I trust my immediate manager to be square with me, but I'm worried that won't matter if the guy above him decides I'm not worthwhile without this certification.
Some clarifications regarding the comments: I do have the job offer. I am a programmer, and a full-time employee. I am of course fighting to keep this certification, but the final decision is out of my hands.