Hi Zeroflag,
I have attached a file for you its a sample base on how to do it, What you need to to do is go in Developers Tab, Select a combo box from ActiveX Control. Once you place Combo Box in desired cell in my case it was A1, but i spread the Combo Box till Cell C1 or D1 to give it extra view (I am not good with formatting), Once placed than right click on combo box and select properties, Set ColumnCount to 3, Set link Cell to A1 and set list fill range to J1:L4, now on developers tab click on design mode to disable it. From this point you should be able to view your options, Cell B1 and C1 can be based on formulas like if, now copy and paste the combo box to your desired list with a macro. I encourage you to look for formatting tools but this should lead you into direction what you are after. Data Validation is only for single column remember!, I hope this helps!