Hi,
you can achevie the through the exception aggretion in BEx designer.
create the minimum and maximum 2 key figures.
ex -1 create the new formula -> put the formula inside -> hit the aggreation tab -> put the minimum -> use the reference char -> invoice date
ex -2 ex -1 create the new formula -> put the formula inside -> hit the aggreation tab -> put the maximum -> use the reference char -> invoice date
now rows panel put product and invoice.
test it the output in RSRT and BEx analyzer.
hope it wil an idea.
Thanks,
Phani.