Don't go to work if you won't be feeling well.
...if you AREN'T feeling well.
I'll have let you know if I think I'm going to be late.
I'll LET you know...
If I'll get a bonus this year, I'm going to go to Hawaii.
If I GET a bonus...
We're going to miss the start if we won't leave soon.
...if we DON'T LEAVE soon.
Could I borrow that book if you won't be using it?
...if you AREN'T using it?
If everything goes well, we'll have been finishing by Friday.
...we'll have FINISHED by...
Let me know if you'll need any help with anything.
...if you NEED help...
If you'll have been there before, you'll know how busy it gets.
If you HAVE BEEN there...