Here's the next part of the puzzle Cell I2:
=IF(Sheet3!A2=Sheet3!A1,Sheet3!E3,Sheet3!E3)

Cell I3:
=IF(Sheet3!A5=Sheet3!A4,Sheet3!E6,Sheet3!E6)

the cell wich the data is fetched from, eg. Sheet3!E3 has to increase be
increments of 3