Catching FileFormat property of .XLAM without confusion with .XLSM - vba

Question

Context
I have developed a .xlam add-in that contains user-data inside. In other words, the user can decide to show the add-in file through a ThisWorkbook.IsAddIn = False to edit the content, which is functional to the add-in itself.
However, the user should not be able to perform some operations when he's/she's working on the add-in's spreadsheets rather than on the normal workbook where the Add-In is running.
Need to check for file extension
From here, it comes my need of checking for the file extension and validate it when some specific "forbidden" procedures might get called. I have made the following tests:
If ThisWorkbook.IsAddIn = True, then ThisWorkbook.FileFormat = 55;
If ThisWorkbook.IsAddIn = False, then ThisWorkbook.FileFormat = 52;
The source of confusion
This is not what I was expecting. By simply executing a FullName request when the Add-In is set visible:
ThisWorkbook.IsAddIn = False
MsgBox ThisWorkbook.FullName
I can read that my file is still named C:\myFile.xlam, even if in that moment is visible to the user. So, I would expect ThisWorkbook.FileFormat to raise a 55 even if visible at run-time. But it doesn't do that, apparently.
The question
I need to make sure to distinguish between modifications on the Add-In (.xlam) and modifications on a possible .xlsm file that the user created, from which is using my Add-In.
Why is the FileFormat of my add-in being equal to the one of an xlsm, if the file is clearly xlam to which is associated a 55 instead of a 52? Where am I being wrong?
EDIT - Example of the action to forbid
On the ribbon there's a button created and added from the add-in, which is connected to a macro that cannot be run into the Add-In. So the check I had in mind was something like this:
If ActiveWorkbook.FileFormat = 55 Then
Exit Sub
End If
However, as said above, this check will not be performed because the Add-In has FileFormat = 52 in the moment in which is set to .IsAddIn = False; hence, even if the ActiveWorkbook is the add-in where I do not want to run the macro, the check will fail and the macro will run anyway.

Answer 1

The .IsAddIn workbook property simply indicates whether the file is being run as an Add-in. It does not change the file format. From the documentation:
When you set this property to True, the workbook has the following characteristics:
You won’t be prompted to save the workbook if changes are made while the workbook is open.
The workbook window won’t be visible.
Any macros in the workbook won’t be visible in the Macro dialog box (displayed by pointing to Macro on the Tools menu and clicking Macros).
Macros in the workbook can still be run from the Macro dialog box even though they’re not visible. In addition, macro names don’t need to be qualified with the workbook name.
Holding down the SHIFT key when you open the workbook has no effect.
I sense that this is the real problem you're trying to tackle:
However, the user should not be able to perform some operations when he's/she's working on the add-in's spreadsheets rather than on the normal workbook where the Add-In is running.
Perhaps it will be best if you can specify what actions you're trying to restrict? There may be a better way to solve this.

Answer 2

For the moment I have found four possible solutions, that I'm going to post here just in case someone would have my same issue:
Comparing the full names - credit to Tim Williams
The "special code" cannot run if the full names are different:
If ActiveWorkbook.FullName = ThisWorkbook.FullName Then
Exit Sub
End If
'"special code"
Comparing the isAddIn property - credit to David Zemens
The "special code" cannot run if this workbook is not currently an add-in:
If ThisWorkbook.IsAddIn = False Then
Exit Sub
End If
'"special code"
Comparing the two objects
The "special code" cannot run if the active workbook is the add-in workbook:
If ActiveWorkbook Is ThisWorkbook Then
Exit Sub
End If
'"special code"
Checking for "xlam" extension
The "special" code will not be run if the extension of the file is xlam:
If Right(ActiveWorkbook.FullName,4) = "xlam" Then
Exit Sub
End If
The four solutions above work fine for the purpose, but the question is still opened : why the FileFormat property changes over the same file depending on ThisWorkbook.IsAddIn being False rather than True?