Auto Populate choices inside MRV variables

Hello - We have the following scenario on a Catalog item.

1) Variable A (type: Look up Select box, 'lookup field value' set to Column A)- Referencing to a custom table. The custom table has 4 columns (Column A, Column B, Column C).

2) Multi Row Variable Set (Variable B (type: look up select box, lookup field value set to Column B) and Variable C (type: look up select box, look up field value set to Column C), both refers to the same custom table  in which was in #1).

The Use case we are trying to fill is;

If a value is selected in Variable A, then the related Column B, Column C values should be displayed in the drop downs of Variable B and Variable C inside the Multi Row Variable. 

Example scenario

Table: u_department

Column A                            Column B                                 Column C

DeptA                                   Michael                               Mike@abc.com

DeptB                                    John                                     John@abc. 

So, if the User selects "DeptA" in Variable A, then Variable B and Variable C inside Multi Row Variable, should show choice values Michael and Mike@abc.com and hide other Department choices. 

Does anyone has come across this requirement and how to approach thus? 

Thanks in advance for any inputs.