In the subreport, put three tablix side-by-side,
Set the row visibility of the first (tablix on the left side) to
=RowNumber(Nothing) Mod 3 =0 OR RowNumber(Nothing) Mod 3 = 2
The middle tablix to
=RowNumber(Nothing) Mod 3 =0 OR RowNumber(Nothing) Mod 3 = 1
The right side to
=RowNumber(Nothing) Mod 3 =1 OR RowNumber(Nothing) Mod 3 =2
and you’ll get:
