Occupation vs. Job vs. Employment vs. Profession
Solution 1:
In the US, Employment and Occupation both refer to having or looking for a job.
If you're looking for a job (any non-specialized job not requiring a particular degree or amount of specialized education), you're looking for employment - temp work, retail sales, etc.
If you have an occupation - it refers to the 'field' or 'type' of work you perform.
People will normally ask, "What's your occupation/profession?" You'd respond, "I'm an accountant." or "I'm a surgeon."
So if there's an Occupation/Profession section somewhere, it's for people who have an education in a specific field of work - nurses, accountants, doctors, architects, etc.
I have never heard the word employment used in the US in the manner Ham and Bacon suggests above.
Solution 2:
I believe that in the context of a job interview, your employment/profession would be what you studied and are qualified for, and your occupation/job would be what it is that you are currently working as.
So if you studied law and are a practicing lawyer, your profession and occupation would be the same thing. However, if you studied law and you are currently working as, say, a bank teller, then your profession/employment would be lawyer, but your occupation/job would be a bank teller.