Hi
Insert any number field as amount (a4) and suppress it for all cells accept summaries.
Now in Summaris right click on a1 total go in Format Field --Suppress --Formula editor and give the following formula :
Whileprintingrecords;
numbervar a1:=Currentfieldvalue;
false;
Right click on a3 summary and go in Format Field--Suppress--Formula editor and write the following formula
Whileprintingrecords;
numbervar a3:=Currentfieldvalue;
false
Now right click on summary of a4 and go in format field --Common Tab--Display String--Formula editor and write the following formula
Whileprintingrecords;
Numbervar a1;
numbervar a3;
if a3 <> 0 then
Currentfieldvalue := a1/a3
else
0