I have a data table and want to create a pivot table off it (top part of image) with a variance field Calculated as the NPV difference (change/movement) between Period D and F (middle part).

I have played around with the calc field, including transforming data, but to no avail (bottom right).

I have manually done the variance of £5k, but would like this as a calc field in the pivot table if possible.

Assume incoming data format is fixed. Open to any ideas, eg powerquery/pivot if can get round.