HLOOKUP seeking True/False Row Then Vlookup (or Index) of True Value against array data set

[Vana_Whyte]

I am asking for help solving a formula solution which searches an active user input cell across a row (no specific column). Which then, depending on it's True/False outcome in the above row formula, then searches the cell value in a Vlookup or index down through an array of known data. ( Most identifiably, I am trying to circumvent the need to have a Data validation drop down variable, which we be used as part of cumbersome "IF" statement to identify the specific customer column # the input value would search against in the Vlookup) Ideally making the tool user friendly, minimizing the amount of user affectable variables)
Snapshot included, notes as follows:
(=If isblank & =iferror are both present)
Row 1: Unique Customer columns
Row 2: Hlookup determining if Row 3 Cell for each column exists in its below column array
Row 3: User Input "Empty" cells
ColA Row 4 : Col M bottom of array row = known data or Empty cells
Cell M4 = where I would like this formula solution to reflect the vlookup/index result of Column M row equivalent
A3:L3 = Would be single cell - simultaneous user input, multiple value results which equate to incorrect data, the issue would be resolved with up-front communication with the user and not need formula circumvention.

If the simple answer is VBA then I guess Data Validation is my band-aid.

Thank you for any help,