continuous tenses

[eliff]

Hello,

It writes in the English books that we can't use 'for' with continuous tenses.
Like this...

I am working at this company for 3 years.
I will be working at this company for 3 years.
I was working at this company for 3 years.

They are incorrect.But,

She must be working at that company for 3 years.
She can be working at that company for 3 years.

My question is:Can we use 'for' with no continuous tenses like that?

Thank you...

[Bennevis]

We can use for in sentences involving the Perfect Continuous:

He has been working there for 20 years.
I've been doing this for 2 years.

[emsr2d2]

Hello,

It writes in the English books that we can't use 'for' with continuous tenses.
Like this...

I am working at this company for 3 years.
I will be working at this company for 3 years.
I was working at this company for 3 years.

They are incorrect.But,

She must be working at that company for 3 years.
She can be working at that company for 3 years.

My question is:Can we use 'for' with no continuous tenses like that?

Thank you...

The preposition isn't the problem sometimes, it's the tense. We simply don't say "I am working here for three years", we say "I have been working here for three years".

The following are fine:

I have just started working here. I will be working here for three years. (Note that this suggests a definite contract of three years' duration and no more).
I started working here in September 2008 so I have been working here for three years.
Next September, I will have been working here for four years.

"I was working at this company for four years" is slightly unnatural. We would use "I worked at/for this company for four years" or "In 2001, I had been working at this company for four years" or "I have been working at this company for four years."

I'm really not sure why any grammar book would say that you can't use "for" with continuous tenses. For subjects such as employment, "for this company", "for twelve years", "for my boss for six months", "for Coca-Cola" etc would be one of the main prepositions we would need.