Returning a column C value list based on context of column A & B

Question

I want to make a contextual drop down menu based on 2 other conditions.

All of my data are in the same table, 3 columns.

The list of results needs to be dependent of the column A first (yellow), and then B (blue), which will list all the results the results in column C (green). I can't seem to be able to do that on the 3rd level (column c in green) and I need help with that.

My Excel is in French so I'll use OFFSET (DECALER) and MATCH (EQUIV) function and the COUNTIFS (NB.SI.ENS) to determine length of the list.

=DECALER(TAB_NOM_DEMO[[#En-têtes];[SUCCURSALE]];EQUIV(TABLEAU_ACC_SUCC[@SUCCURSALE];TAB_NOM_DEMO[SUCCURSALE];0);
  EQUIV(TABLEAU_ACC_SUCC[[#En-têtes];[TYPE DEMO]];TAB_NOM_DEMO[#En-têtes];0);NB.SI.ENS(TAB_NOM_DEMO[SUCCURSALE];
  TABLEAU_ACC_SUCC[@SUCCURSALE];TAB_NOM_DEMO[TYPE DEMO];TABLEAU_ACC_SUCC[@[TYPE DEMO]]);1)

My problem that I see right now is that the start cell:

TAB_NOM_DEMO[[#En-têtes];[SUCCURSALE]]

needs to be variable of column A first, then column B to get the right data in column C.

I'm not sure I'm using the right function right now so I'm open to suggestions.

Update

I had great results with the FILTER function so far. It works well in a test cell, I only the results I need to see. But I can't make it happen in data validation list... why?

=TRIER(FILTRE(TAB_NOM_DEMO[NOM DEMO];
 (TAB_NOM_DEMO[SUCCURSALE]=TABLEAU_ACC_SUCC[@SUCCURSALE])*
 (TAB_NOM_DEMO[TYPE DEMO]=TABLEAU_ACC_SUCC[@[TYPE DEMO]])))