Steps that i envisage
Load the smartsheet with predetermined data - say columns A to G
Create form for displaying columns A to D only and allow entry of column J and K
Create form for displaying columns A to D only and allow entry of column M and N
Create a workflow where person A is asked to complete cols J & K when col H = "John" using Form 1
Create a workflow where person B is asked to complete cols J & K when col H = "Mary" using Form 1
Create a workflow where person C is asked to complete cols M & N when col L = "Pat" using Form 2
Is this possible ?