Copying Down GetPivotData Formula

Sorry to ask such a basic question, however it is eluding me.

I have a pivot chart that is comparing the same data elements from 2 different dates to find the difference between the two.

I am trying to set up a way to automatically calculate this difference, however it is proving to be more complex than i thought.

I have tried entering a simple GetPivotData formula subtracting one from the other in an adjacent column, however am then unable to copy this down the many rows, as the row reference stays at row 1 in the table, it does not increment as i copy it down.

I also thought there may be a way to have an additional column within the pivot that will show the difference, but cant find that one either.

any ideas?

Sorry .... example attached

I am looking to get the difference between the 2 dates in column B and C, and also the difference between columns D and E.

Thanks debraj_patra1 ...... that result is almost what i was after.

Are you able to step me through how it is done? I found the calculate4d item and calculated field options in the ribbon, however am not quite sure how to implement it.

On your example, if i change the dates in the columns filter, it is still calculating the original dates of 22/4 - 15/4, despite me having changed the dates to be 22/4 - 18/4.

Is there a way to have this so when the dates are changed the calculation is done on the new values? I understand i may have to refresh manually.

Thanks in advance

Darren.