how to avoid divergent edits?

[g]

how do you recommend i solve this problem:

the director sends a spreadsheet to members of the board, several of
them reply with changes, the director then has several divergent
versions of the spreadsheet to reconcile.

possible groupware solutions?:  twig?  phpgroupware?  egroupware? 
skyrix?  ensemble?  lotus notes?  other?

i'd like to hear of experience with any of the above, or other better
ways to address the issue, or pointers to similar discussions.

tia,
greg