1.Add group 39,then get group a,group b,...,(assume 40 rows per page)
2.Declare a varior such as intRows
3.In Page head part ,U must clear intRows, such as intRows:=0
4.In detail part, u must add intRows:=introw+1 to total all rows of detail rows current page
5.Show or hide group a,group b,...
6.Result is show blank rows with line(group a,group b,...)