In reply to Jettison:
> I've done a couple 4000m climbs in the past couple months. I felt fatigued on the first and a little nauseous on the second. The first I spent one night at 2500m and the second at 3500. Did pretty good.
> The second I only spent one night at 3000m and woke up feeling a bit crappy but after getting some air moving I felt a lot better.
> I'm worried about acclimatizing with Blanc as I have never been that high.
> Yes I will be on my own for the first 4 days. So I wonder if Cosmiques wil be too risky on my own.
It's not just acclimatisation but, ideally, rest as well. Personally, I'd just rest and eat the day before starting up MB. From what you say, I think you will feel pretty grotty on MB. With enough determination you will probably get up it, but it might not be a pleasurable experience.
Ideal preperation would be, say, 2 days to do the Aiguille du Tour from the Albert Premier Hut. Then, perhaps, 2 days to do MB du Tacul from the Cosmiques. Then a day's complete rest. That's five days and two glaciated peaks, where you'll need a guide or partner.
As others have said, if you're on your own and only have four days, you can't really acclimatise for MB. So, you'll have to suffer for your art, as it were.