It sounds like you need to create a “Lookup FlowField”. This video should help: https://www.youtube.com/watch?v=gnq2PUSozDU
But your problem is going to be, that the footer elements do not have a table where you can add a FlowField, most of them uses the “Integer” table. So the current method of adding fields with SOD doesn’t work for that.
You will probably need to engage an AL developer…