Prevent duplicate entry in excel.

On the Settings tab, choose "Custom" from the Allow drop down list and enter =COUNTIF($D:$D,D2)=1 into the Formula box

Office 2021 Activation using command

 @echo off

title Activate Microsoft Office 2021 (ALL versions) for FREE - office.com&cls&echo =====================================================================================&echo #Project: Activating Microsoft software products for FREE without additional software&echo =====================================================================================&echo.&echo #Supported products:&echo - Microsoft Office Standard 2021&echo - Microsoft Office Professional Plus 2021&echo.&echo.&(if exist "%ProgramFiles%\Microsoft Office\Office16\ospp.vbs" cd /d "%ProgramFiles%\Microsoft Office\Office16")&(if exist "%ProgramFiles(x86)%\Microsoft Office\Office16\ospp.vbs" cd /d "%ProgramFiles(x86)%\Microsoft Office\Office16")&(for /f %%x in ('dir /b ..\root\Licenses16\ProPlus2021VL_KMS*.xrm-ms') do cscript ospp.vbs /inslic:"..\root\Licenses16\%%x" >nul)&echo.&echo =====================================================================================&echo Activating your product...&cscript //nologo slmgr.vbs /ckms >nul&cscript //nologo ospp.vbs /setprt:1688 >nul&cscript //nologo ospp.vbs /unpkey:6F7TH >nul&set i=1&cscript //nologo ospp.vbs /inpkey:FXYTK-NJJ8C-GB6DW-3DYQT-6F7TH >nul||goto notsupported
:skms
if %i% GTR 10 goto busy
if %i% EQU 1 set KMS=kms7.office.com
if %i% EQU 2 set KMS=e8.us.to
if %i% EQU 3 set KMS=e9.us.to
if %i% GTR 3 goto ato
cscript //nologo ospp.vbs /sethst:%KMS% >nul
:ato
echo =====================================================================================&echo.&echo.&cscript //nologo ospp.vbs /act | find /i "successful" && (echo.&echo =====================================================================================&echo.&echo #Please consider supporting this project: donate to my paypal "devomman@gmail" &echo #Your support is helping me keep my servers running 24/7!&echo.&echo =====================================================================================&choice /n /c YN /m "Would you like to visit my blog [Y,N]?" & if errorlevel 2 exit) || (echo The connection to my KMS server failed! Trying to connect to another one... & echo Please wait... & echo. & echo. & set /a i+=1 & goto skms)
explorer "https://www.office.com/"&goto halt
:notsupported
echo =====================================================================================&echo.&echo Sorry, your version is not supported.&echo.&goto halt
:busy
echo =====================================================================================&echo.&echo Sorry, the server is busy and can't respond to your request. Please try again.&echo.
:halt
pause >nul


Source: https://gist.github.com/AneurysAdames/2bcbfc58707168a0bc87c2754f62014a