Excel - dynamic data validation lists for multiple rows - arrays

Question

Excel 16.x for Mac
I have a situation where we have a tabular spreadsheet template for requisitions. The spreadsheet is copied for each project and filled out. Each spreadsheet will have multiple rows - from 1-400. Each row has columns with data validation rules.
The issue is that I cannot figure out how to enter a formula that generates a different list for each row the data validation formula entry.
eg:
Each row will have a "Facility Code" and a "Building Code". The "Building Code" list is generated by what is in the "Facility Code" cell. The problem is that the data validation rule wants a range of cells, not a formula that generates an array. With sometimes 400 rows, I would need to create 400 different lookups based on the R(n):Facility_Code entry.
Dynamic List for Facility Code (in Template!P4):
=UNIQUE(FILTER(NFS_Facilities[Facility Code],(NFS_Facilities[Facility Code]<>""),""))
Dynamic List for Building Code:
=UNIQUE(FILTER(NFS_Facilities[Facility Code],(NFS_Facilities[Facility Code]='Template'!P4),""))
The P4 is the issue here as it will change by the row.
The Data List validation points to a range of cells.
The current behavior is on R1, it works fine. On R2, no matter what is entered into "P5", it generates the data based on P4 (as it should as that is what is in the formula).
Is there any way to have the Data Validation formula be dynamic based on the R(n)? The intent is to have the Data Validation range be a dynamic formula replacing P4 with tableName[facilityCode]

Answer 1

...Ignore my previous answer.
Putting a FILTER isn't going to work inside a DV with a dynamic reference for some reason.
You'll need a hidden sheet, and in that sheet each row on the input sheet will have a corresponding row of options. They key is to use =TRANSPOSE() around the FILTER() to make the results in rows not columns (so they don't cause #SPILL! errors.
Once you have that setup, just point the DV to the sheet with a spill reference (with a # behind it): example in Sheet BUILD_CODE_OPTIONS!A4:
=TRANSPOSE(UNIQUE(FILTER(NFS_Facilities[Facility Code],(NFS_Facilities[Facility Code]='Template'!P4),"")))
then in the DV for the Building Code field on row 4:
BUILD_CODE_OPTIONS!A4#
You'll need a sheet for every column you want a dynamic drop down in.
... now just waiting for MS to fix the bug preventing the FILTER in the DV ...