The text in this text box specifies the mathematical expression that is used to
select data rows in the data table for use in the data-sequence
generation. The expression usually contains the built-in variables Row that
is evaluated to the row number of the original data table and IDX
that is evaluated to the index of the current data table
of the generated data sequence. For a
specific data row in the original data table and a specific data table of
the generated data sequence, if the expression is evaluated
to true, then the data row is copied from the original data table into that
specific data table of the generated data sequence; otherwise, the data row
is not used for that specific data table of the generated data sequence.
