Dynamic Worksheet Title Reference Optimization - excel

Question

Scenario: I have a workbook that needs to be able to dynamically reference different worksheets based on user input. I was able to achieve this by using several INDIRECT functions and some other basic functions such as INDEX.
My problem is that the workbook is taking several minutes to load on a fairly powerful computer with no other strenuous processes running.
Question: Is there a simple way to optimize workbooks? I tried looking online for some standard methods to run through to catch unnecessarily strenuous processes to no avail. I am willing to use VBA if it would help speed the sheet up.
Thanks

Answer 1

Don't use INDIRECT or any other volatile functions (OFFSET, RAND, NOW, TODAY) in your workbooks if you can help it, because they get recalculated automatically pretty much at the drop of a hat...even if you’re doing something to the workbook that has absolutely nothing to do with those formulas whatsoever, such as:
Entering new data in a completely unrelated cell
Editing any existing, completely unrelated cells
Deleting or inserting a row or column anywhere in the workbook
Performing certain AutoFilter actions
Double-clicking a row or column divider (in Automatic calculation
mode)
Adding, editing, or deleting a defined name
Renaming a worksheet
Changing the position of a worksheet in relation to other worksheets
Hiding or unhiding rows (but not columns)
This means that if you have lots and lots of volatile functions like OFFSET or INDIRECT in your formulas, those formulas are going to be recalculating pretty much constantly. And if those formulas do some pretty resource-intensive number-crunching, Excel will be re-crunching those numbers pretty much every time you touch the mouse or keyboard. Yikes!
But that’s not the half of it: After Excel recalculates those functions, it merrily starts recalculating all cells downstream of them—regardless of whether those downstream cells have volatile functions in them. And regardless of whether anything actually changed as a result. And I mean all cells...not just the cells that directly point to your volatile functions but all the cells that point to those cells, and then the next bunch of cells that point to that last bunch, and so on and so on, all the way through your workbook. If you’ve used volatile functions at key points within a spreadsheet, pretty much the entire spreadsheet could be recalculating constantly. Double yikes!
But even this is not the worst of it! The problem isn’t limited to the workbook you happen to be doing something with at the time. Rather, every volatile function in every open workbook gets recalculated when you make a change in any workbook anywhere—even if there aren’t any formula links between those workbooks. So if you’ve got a very large spreadsheet model with volatile functions open—and then you start typing, say, a shopping list in another, it could take minutes for you to add each item to that shopping list, as everything you type in the shopping list triggers a new avalanche of unnecessary and pointless recalculation in the large spreadsheet model. Triple yikes!
The fact that each and every cell downstream of any volatile functions get recalculated is an important point to get your head around. Many people think that just the volatile functions themselves get recalculated. They are mistaken. It’s the subsequent forced recalculation of all cells downstream of all volatile functions in all open workbooks that causes you grief. In fact, even just one volatile function in one workbook could cause you grief if you have a very long calculation chain hanging off it.
What to use instead?
Use INDEX, or even better, CHOOSE.
Note that while INDEX isn’t fully volatile, it ain’t perfect: It still gets recalculated whenever the workbook opens. This is known as is semi-volatility, and it means that you still might notice recalculation delays when initially opening a complicated model that uses INDEX. Which is one of the reasons I go for CHOOSE
=CHOOSE(index_num,value1,value2,...)
Here’s the translation from Microsoft-speak into Jeff-speak:
=CHOOSE(Which area do you want?, First area, Second area, ...)
You need to translate your dropdown choice into a number in order to drive the Which area argument. But that’s no problem; you just use exactly the same setup as you do for INDEX—a lookup table that converts the output of the dropdown into an index number that tells CHOOSE which range you want.
If your input areas are turned into Tables, then great...you can just use the Table names.