[clivehawkins]

Sorry, I obviously misunderstood your question. I thought you were asking when we use the progressive form OTHER THAN for the future.

Very briefly, other future forms are:
1. 'Going to' for intentions\plans. eg I'm going to have a party for my 18th birthday. (It's my intention to do this but as yet nothing has been arranged.) Compare this to I'm having a party for my 18th (It has been arranged\confirmed). It's also used for predictions. eg John's driving very fast and it's raining. He's going to crash.

2. 'Will' is used in a variety of ways. a) Also for predictions. eg I think Polly will fail her exam. b) For promises eg I promise I'll call you when I get there. c) offers of help eg 'I'm stuck on my homework.' 'Don't worry, I'll help you'. d) Spontaneous decisions. eg 'Did you know that U2 are playing next month?' 'Really! I'll get us a couple of tickets!'

3. Present simple. This is used for timetables and fixed schedules. eg The London-Liverpool Express leaves at 21.00 and arrives just before midnight. Don't be late - the lesson starts at 15.00.

That's just a brief outline. I suggest you check a reference book for a more detailed explanation.

Hope that helps.