Back references:
PublicApi

mSetCellContent

parameter	format	requirement	notes
row	integer	required	table row
column	integer	required	table column
newValue	whatever the type of the cells content is	required	new content for the cell
relative	boolean (integer)	optional (default = false)	whether the values for row and columns are treated absolute or relative (sorting or filtering may change the order)
recalc	boolean (integer)	optional (default = true)	recalculate columns widths (time consuming as every cell in the column must be rendered)
tablename	string	optional (default = tablelist[1])	name of the table (only necessary if behavior hosts more than one table => 3-D sprite)

So "mSetCellContent" is the way to go. "It will take care of refreshing the cell and recalculating columns, if necessary", but:

Can I use it to add cells to an already built table?

How do I change other parameters, not just content? (and besides selection, hilight and enabled/disabled that have their own methods); for instance text format.