This example is a little different than a rolling 12 month average as those are always the prior 12 months regardless of Actual or Forecast data.
This example will leverage work done in another asset where we fill all forecast months with a 1, this helps us determine the first month with non actual data which is key to our example:
“Low Maintenance Way to be able to Reference the First Non-Actual Month (sort of Start of Plan) in a Formula”
Once we know the first month of forecast we will be able to set up the logic we need to answer this question. For this example we will use our 6360 Office Supplies expense account.
(ASSUM.IsPlanPeriod - ASSUM.IsPlanPeriod[time=this-1]) > 0,
ACCT.6360_Office_Supplies[time=this-12:this-1] / 12,
NOTE: Normally it is not good to use / for dividing nor hard coding in a number but since the number of months in the year is unlikely to change or ever be zero it is acceptable to break the rule for this example.
You can see that we have the desired outcome.