I am attempting to select an option from a single-select drop-down that will auto-fill the next column. 

I have loaded the formula as a one to one basis, i.e. if 'this person' is selected, populate 'this manager' in the next column. However, I need it to be across multiple employees. So if, this person, this person, or this person is selected, auto-fill this manager. If I attempt to add an 'or' into my formula, I'm getting error messages of UNPARSEABLE or INCORRECT ARGUMENT SET

Here is my one to one formula:




Have you considered doing a vlookup from a new sheet? It might be an easier approach. You'd only have to manage a column of employees, and in column two list their managers. Then do a vlookup from your dropdown cell with a cross-sheet reference to the vlookup table. 

If you use an IF formula you are going to have to update that formula everytime a person changes managers, or a new person is added to the team and that would make for a lot of work in your sheet. 

IF you absolutely want to use a formula, try this method... 

IF(OR(Engineer1 = "This person", Engineer1 = "This person", Engineer1 = "This person"), "This manager", IF(OR(Engineer1 = "This person", Engineer1 = "This person", Engineer1 = "This Person"), "This Manager"))

That's going to get unweildy really fast.