If you have a complicated formula and it is giving you an error or not the answer you expected, Excel has an Evaluate Formula tool.
This is available from the tools menu under Formula Auditing or from the Formula Auditing toolbar shown here. The evaluate formula button is on the right.

This tool evaluates each part of the formula in turn showing you how outcomes. It is then possible to see where your error or unexpected result is coming from.

Here is a tip from Allen Wyatt’s Excel tips site.

Allen was asked if there is a way to selectively load add-ins for specific worksheets. He said there is a way to do this, but it involves the use of macros attached to the Workbook module for the specific worksheets. Follow these general steps:

1. Load the worksheet for which you want a specific add-in loaded.
2. Press Alt+F11 to display the VBA Editor.
3. Double-click on the “This Workbook” object in the Project Explorer. Excel opens a code window for This Workbook.
4. Place the following macros in the code window:

Private Sub Workbook_BeforeClose(Cancel As Boolean)
AddIns("Add-In Name").Installed = False
End Sub

Private Sub Workbook_Open()
AddIns("Add-In Name").Installed = True
End Sub

1. In the code, change the name of the add-ins (“Add-In Name”) to the real name of the add-in you want to use with the worksheet.
2. Close the VBA Editor.
3. Save your worksheet.

I will be using this method to choose which addins I have loaded at any one time. I have up to three loaded at one time which I don’t need all the time. Thanks Allen