You can cluster your "on change of" field in a formula to return a certain number of values per group, and then insert a group on this, and place the chart in a group section. If you have a sequential field, it is simple. Otherwise, sort your records in order of the "on change of" field, and then insert a group on this formula:
whilereadingrecords;
numbervar cnt := cnt + 1;
numbervar i;
numbervar j;
for i := 1 to 2000 do( //replace 2000 with a number larger than the count of your "on change of" field
if cnt in 20*i-19 to 20*i then
j := i
);
j
Then place your chart in the group section.
-LB