What Had Been Happening Before Something Occurred
Past Perfect Continuous
The past perfect continuous expresses the duration of an activity up to another point in time in the past. The use of the past perfect continuous stresses that a certain activity had been going on before something important happened.
Example:
How long had you been studying information technology before you decided to switch to finance?
How long is it going to take them to decide on the take over bid so we can start real work
How often had you been checking your safety deposit box prior to the break-in?
Positive Form:
Subject + had + been + 'ing' form of verb + (object(s)) + time expression
She had been working on the fixed exchange rate report for five hours when he asked for it.
Negative Form:
Subject + had + not + been + 'ing' form of verb + (object(s)) + time expression
They hadn't been using that credit card account long when they used up their card's limit.
Question Form:
(Question Word) + had + subject + been + 'ing' form of verb?
How long had you been studying information technology before you decided to switch to finance?
Past Perfect Contrasted with Past Perfect Continuous
The past perfect expresses something that finishes before another activity in the past. The past perfect continuous, on the other hand, expresses the duration of an activity at the moment something important happened in the past.
Past Perfect Examples:
Had you confirmed the final balance prior to computing the profit and loss figures?
He hadn't kept his account for long before it was cancelled.
Past Perfect Continuous Examples:
She had been working on the fixed exchange rate report for five hours when he asked for it.
She had been doing well financially until she wrote a bank draft for more than was in her account.