I could've sworn I'd already asked a similar question here, but I can't find it. And now I have, I believe, a more precise set of questions about it.

Topic Number: 513 - Work-Related Education Expenses says:

You may be able to deduct work-related education expenses paid during the year as an itemized deduction on Form 1040, Schedule A (PDF), Itemized Deductions. To be deductible, your expenses must be for education that (1) maintains or improves your job skills or (2) that your employer or a law requires to keep your salary, status, or job. However, even if the education meets either of these tests, the education can't be part of a program that will qualify you for a new trade or business or that you need to meet the minimal educational requirements of your trade or business.

What exactly, according to the IRS defines a "new trade or business"?

Just how broadly does the IRS see this?

As a software developer who only currently uses Visual Basic, would it be a new trade if I learned another language like C? I mean, sure, it could qualify me for more jobs, but is it a new trade or business?

Considering I'm self-taught and some corporations might not be willing to hire me right now, would taking a course that made it so that they would hire me (but with a very similar job title) disqualify me for writing an education expense off? Does that mean I need it to meet the minimal educational requirements of my trade or business and thus can't write it off?

Where is the line?