Excel 2007 and later add-in files: registry value xlamfilesUserHKCU\software\policies\microsoft\office\16.0\excel\security\fileblock

Policy ID: L_Excel2007AndLaterAddInFiles
Scope: User Configuration
Supported on: At least Windows Server 2008 R2 or Windows 7
Source: Microsoft 365 Apps / Office Administrative Templates (version 5568.1000)
Category: Microsoft Excel 2016 › Excel Options › Security › Trust Center › File Block Settings

Registry

xlamfiles

REG_DWORDUser

HKCU\software\policies\microsoft\office\16.0\excel\security\fileblock Current key

Enabled value: Depends on the option value
Element: File block setting:

Options
Item	Stored value
Do not block	0
Save blocked	1
Open/Save blocked, use open policy	2

Apply with .reg · CMD · PowerShell

.reg

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\excel\security\fileblock]

; Options (use only one)
; Do not block
"xlamfiles"=dword:00000000
; Save blocked
"xlamfiles"=dword:00000001
; Open/Save blocked, use open policy
"xlamfiles"=dword:00000002

CMD

:: Options (use only one)

:: Do not block
reg add "HKCU\software\policies\microsoft\office\16.0\excel\security\fileblock" /v "xlamfiles" /t REG_DWORD /d 0 /f
:: Save blocked
reg add "HKCU\software\policies\microsoft\office\16.0\excel\security\fileblock" /v "xlamfiles" /t REG_DWORD /d 1 /f
:: Open/Save blocked, use open policy
reg add "HKCU\software\policies\microsoft\office\16.0\excel\security\fileblock" /v "xlamfiles" /t REG_DWORD /d 2 /f

PowerShell

# Common: create the key
New-Item -Path 'HKCU:\software\policies\microsoft\office\16.0\excel\security\fileblock' -Force | Out-Null

# Options (use only one)
# Do not block
New-ItemProperty -Path 'HKCU:\software\policies\microsoft\office\16.0\excel\security\fileblock' -Name 'xlamfiles' -PropertyType DWord -Value 0 -Force | Out-Null
# Save blocked
New-ItemProperty -Path 'HKCU:\software\policies\microsoft\office\16.0\excel\security\fileblock' -Name 'xlamfiles' -PropertyType DWord -Value 1 -Force | Out-Null
# Open/Save blocked, use open policy
New-ItemProperty -Path 'HKCU:\software\policies\microsoft\office\16.0\excel\security\fileblock' -Name 'xlamfiles' -PropertyType DWord -Value 2 -Force | Out-Null