I am managing an Excel VSTO add-in that works on specific files and does not support inserting/deleting columns.
I would like to prevent the user from being able to do so in order to secure data in the files.

• I tried to Protect() sheets through C#, however it only locks column insertion/deletion if you also lock the content, which I cannot do
• I tried using AppEvents and more specifically SheetChange, but haven't found a way to cancel the change. I believe there is none but let me know if I'm wrong
• I am aware that an Undo package exists somewhere but haven't looked whether it works with events because:
  • I would prefer to avoid external packages
  • Undo() in my situation would trigger-chain SheetChange which obviously doesn't work without adding extra complexity

Is there a way to prevent column insertion/deletion in Excel sheets, through C# specifically, without locking anything else and if possible in a simple manner?
Thanks.

EDIT - UPDATE
I have been setting up a makeshift solution so far which I'll share here:

AppEvents_SheetChangeEventHandler EventSheetChangeHwnd;

private void ThisAddin_Startup(object sender, EventArgs e)
{
    Application.SheetChange -= EventSheetChangeHwnd;
    EventSheetChangeHwnd = new AppEvents_SheetChangeEventHandler(SheetChange_Event);
    Application.SheetChange += EventSheetChangeHwnd;
}

private void SheetChange_Event(Object Sh, Range Target)
{
    if(!Target.Address.Equals(Target.EntireColumn.Address)) // Can use Target.Row != 1 too to check faster and remove unwanted occurences
        return;

    Application.EnableEvents = false; // Prevents event from re-firing after undo
    Application.Undo();               // Native undo method
    Application.EnableEvents = true;

}

Now this isn't a proper solution because:

• The event fires every time a value is changed in the sheet, if you're writing data cell by cell it will fire every time and can get to a point where you see a drop in processing speed
• It will fire if a whole sheet or a whole column is copy pasted - basically it doesn't check specifically for column insertion/deletion
• Having to use Application.EnableEvents could have side effects and actually requires more code to handle properly