This user's problem is not about Excel 2010. It is about a deeper limitation of the spreadsheet model itself. When you have to manually manage which cells are "live" and which are "N/A" based on a case selector, you have hit the wall where static grids stop cooperating and start fighting you.
Here is what is actually happening: The user has built a logical workflow, two equations, two sets of variables, a clear case selector in column E. That is a good foundation. But the spreadsheet is a blank canvas, not a smart document. It does not know that when you choose Case 1, columns O through U should automatically become inert. It does not understand that "N/A" is a state of the data, not a value you type in. So the user is left trying to trick conditional formatting into writing text into empty cells, which Excel 2010 simply will not do. The tool refuses to acknowledge intent unless you first commit a manual action.
This is the friction that millions of spreadsheet users accept as normal. They learn workarounds, helper columns, VBA macros, manual data entry protocols, instead of asking why the tool cannot adapt to the logic they already defined. The user here has already defined the logic. The spreadsheet should be able to read that definition and adjust the interface accordingly. That is not a revolutionary idea. It is a basic expectation for any tool that claims to handle structured data.
What this means for you is straightforward: If you find yourself writing conditional formatting rules to hide or label cells that your own data model says are irrelevant, you are working against the grain of your tool. The real solution is not a clever formula hack. It is a spreadsheet that understands equations as first-class objects, one where you can define a case selector, assign variable ranges per case, and have the grid show exactly what is usable for that case, nothing more. The user should not have to fight Excel 2010 to get "N/A" into a cell. The tool should know that when Case 2 is active, column F through N are not part of the equation, period.
Our opinion is plain: Stop treating your spreadsheet as a passive grid. Demand that it reflect your logic, not the other way around. The user already did the hard part, they defined the cases and the variables. The next step is using a tool that honors that structure automatically.