Custom Column - Applying Row Level Security/Visibility Based on Criteria

I have a custom column where if a certain product line is present on that row I want to code it to a different business unit and allocate values to it accordingly, otherwise I want it to reference a related function which I have that is pulling another value from another table in my query. I'm trying to publish this report to a group that I'd like to restrict visibility / access based on this 'True Region' formula below, but am uncertain how to accomplish this.

If I use row level security and apply it to the 'Region Name' from my Customer_Master table I ultimately display the wrong values that I'm trying to reallocate. Anyone have a workaround here to correctly filter this data?

My formulas are as follows;