How to change dynamically the From hdr?

[Ennio-Sr <nasr.laili@xxxxxx>]

[Using mutt 1.5.18-6 under GNU/Linux Lenny, from console]

Hi all,
I found many old posts explaining how to choose a different From header
from a list of From hdrs while composing a message, but was unable to
use them. 
For sure something changed in mutt from year 2003, which was the date of
latest messages; however I doubt that using 'vim' as a mutt editor makes
all such instructions unusable.
Is there any workaround?

Thanks for your attention, 
-- 
[Why use Win$ozz (I say) if ... "even a fool can do that.          \\?//
 Do something you aren't good at!" (as Henry Miller used to say)]  (°|°)
Regards, Ennio. --> Please replace '.' for '_dot_' in my Reply-To.  )=(