Hi @rory.grant ,
Currently I don’t see any column in your code related to the previous period.
However, if you will implement this you can indeed use rollforward. Let’s say you create variable custom.[row_title_key].value_py to refer to the value of the previous period. Your rollforward code can look like this:
{% rollforward custom.[row_title_key].value_cy custom.[row_title_key].value_py %}
{% rollforward nil custom.[row_title_key].value_cy %}
Keep in mind that default values are never part of a rollforward. If you want to be sure you have the same value as in the previous period, make sure to recreate the default that was used there.
You can find more information on the rollforward functionality here.
Kind regards,
Michiel