Hi
you can "unmerge" the cells - but if in the merge some data was deleted
then, no i don't believe you can "undo" the merge & centre option and get
the deleted data back.
to unmerge cells - if you're using version 2002 and above just click on the
merge & centre icon again - for previous version, just select the merged
cells, choose format / cells, go to the alignment tab and uncheck merge
cells option and then change the alignment to whatever you want.
hope this helps
Cheers
JulieD