FormatableBitSet colList = new FormatableBitSet(2);
colList.set(1); // update first row column 1, the second column
int slot1 = page.getSlotNumber(rh1);
page.updateAtSlot(slot1, partialRow.getRow(), colList);
colList.clear(1);
colList.set(0); // update second row column 0, the first column
int slot2 = page.getSlotNumber(rh2);
page.updateAtSlot(slot2, partialRow2.getRow(), colList);
// verify the update worked.