Hi Daniel,
you should always include ALL requirements in your post, oterwise we don´t give you the correct solutions.
If you want to use columns, which will not be available for all months, it becomes complicated.
So you could create the now 39 columns - which will be necessary if there is a calculation to be done in the query.
You can also try to create your additional columns, which will work if the data is available not if you need to calculate in the query.
The put a restriction for only the current month using a variable into those 3 new columns
For all months which are not the current one, those 3 columns will stay empty. Then you can hide those by hiding 0-columns.
regards
Cornelia