将来进行时
基本形式：will be doing；be going to be doing
用于描述未来将会发生并且会持续一段时间的动作。

过去完成进行时
基本形式：had been doing
用于描述一些开始于过去并结束于过去的动作。常与“for five minutes”“for two weeks”之类的短语搭配。

例句对比：
（1）
They had been talking about this problem for 2 hours before Tony arrived.在托尼到之前，他们已经谈论这个问题谈了2小时了。
They will be talking about this problem tomorrow.明天他们会谈论这个问题。

（2）
She had been working at that company for three years when it went out of business.在公司停业之前她在这工作了3年了。
She will be working at that company in three years.3年内她都会在这个公司工作。

（3）
Mike wanted to sit down because he had been standing all day at work.麦克想要坐下，因为他为了工作站了一天了。
Mike will be standing all day tomorrow.麦克明天要站一天。

（4）
James had been teaching at the university for more than a year before he left for Asia.詹姆斯离开亚洲之前已经在这个大学教书超过一年了。
James will be teaching at the university.詹姆斯将会在这个大学任教。

（5）
I had been looking for it for days before I found it.我找这个东西找了好久了。
I will be looking for my book tonight.我今晚会找找我的书。

（6）
I had only been reading a few minutes when he came in.我刚看了几分钟他就进来了。
I will be reading books in 2 hours.两小时内我都会在看书。

同样是进行时，从以上例子想必能很清楚的分辨出两个时态的区别。