want to calculate price for the materials listed per page of main window

dear friends,

i want to calculate amount for the items listed on respective page.I have main windw in which items are been listed.i m getting amount for items listed on first page at last but in second page i get the sum of previous and this pages item price too.

i want to calculate amount for all items listed per page on each page seperately...

please help....

thnx in advance..