[susan53]

Whether the future event is near or far makes no difference - other concepts are involved :

1. Will expresses a mental concept - an idea in my mind. This may be
a) a logical prediction : Don't drink so much coffee. You'll be awake all night.
b) an expression of willingness - as in your example, I'll help you now.
Whether the action is immediate or in the far distant future makes no difference.
I'll help you now or When you have your first baby, I'll help you look after it.

2. BE + Ving is used to express an on-going action, and (for English) the action starts as soon as it is arranged. So I'm seeing David next week ( = we made the appointment yesterday, so the action has now "started" and will be on-going until I arrive in David's office).
Again, it doesn't matter if it's immediate or in the distant future, as long as the arrangement, or at least a firm decision has already been made : When I retire in fifteen years time, I'm moving back to London.

So don't worry about when the action will happen. Think instead of the concept underlying it : is it "just an idea in your head" ? In this case, use will. Or is it something that has already been arranged by eg making an appointment or an agreement with someone else, buying tickets etc. In this case use BE + Ving.

There are other ways of expressing the future too of course, and each way expresses a different concept. A lot of these have already been covered on the forum. For example, if you go back to 19th November 2006 you'll find a post on Will vs Be going to do (at the time of writing it's on page 12).