Using only standard commands, I have scripted LocalGroup.bat to add or delete users to/from a local group.

The syntax for using LocalGroup.bat is:

LocalGroup Computer LocalGroup User AorD OK

Where:

Computer   is the NetBIOS computer name where the LocalGroup exists, like JSI007.                              LocalGroup is the local group name on Computer, like Administrators or "Power Users".                              User       is the local or domain user, using the "ComputerName\LocalUserName" or "DomainName\DomainUser" format,                                         like JSI007\Administrator or "JSIINC\Jennifer".                              AorD       is the action switch, A is Add and D is delete.                              OK         is a call directed environment variable that will contain a                                         Y if the maintenance was successful, or a N is the maintenance failed.                                         A message is displayed with one of these failure reasons:                                             The network path was not found.                                             The specified local group does not exist.                                             The user name could not be found.                                             The specified account name is not a member of the local group.                                             The specified account name is already a member of the local group.
LocalGroup.bat contains:
@echo off                              setlocal ENABLEDELAYEDEXPANSION                              if \{%5\}==\{\} goto err1                              set Comp=%1                              set Group=%2                              set User=%3                              set AorD=%4                              if /i "%AorD%" EQU "a" goto vbs                              if /i "%AorD%" NEQ "d" goto err2                              :vbs                              if exist "%TEMP%\LocalGroup.vbs" goto doit                              @echo.Dim Oargs, strComputer, strGroup, strUser, AorD>"%TEMP%\LocalGroup.vbs"                              @echo.Set WshShell = CreateObject("WScript.Shell")>>"%TEMP%\LocalGroup.vbs"                              @echo.Set oArgs = WScript.Arguments>>"%TEMP%\LocalGroup.vbs"                              @echo.strComputer = oArgs(0)>>"%TEMP%\LocalGroup.vbs"                              @echo.strGroup = oArgs(1)>>"%TEMP%\LocalGroup.vbs"                              @echo.strUser = oArgs(2)>>"%TEMP%\LocalGroup.vbs"                              @echo.strUser = Replace(StrUser,"\","/")>>"%TEMP%\LocalGroup.vbs"                              @echo.AorD = oArgs(3)>>"%TEMP%\LocalGroup.vbs"                              @echo.if lCase(AorD) = "a" then>>"%TEMP%\LocalGroup.vbs"                              @echo.  Set objGroup = GetObject("WinNT://" ^& strComputer ^& "/" ^& strGroup ^& ",group")>>"%TEMP%\LocalGroup.vbs"                              @echo.  Set objUser = GetObject("WinNT://" ^& strUser ^& ",user")>>"%TEMP%\LocalGroup.vbs"                              @echo.  objGroup.Add(objUser.AdsPath)>>"%TEMP%\LocalGroup.vbs"                              @echo.  Wscript.Quit>>"%TEMP%\LocalGroup.vbs"                              @echo.End If>>"%TEMP%\LocalGroup.vbs"                              @echo.if lCase(AorD) = "d" then>>"%TEMP%\LocalGroup.vbs"                              @echo.  Set objGroup = GetObject("WinNT://" ^& strComputer ^& "/" ^& strGroup ^& ",group")>>"%TEMP%\LocalGroup.vbs"                              @echo.  Set objUser = GetObject("WinNT://" ^& strUser ^& ",user")>>"%TEMP%\LocalGroup.vbs"                              @echo.  objGroup.Remove(objUser.AdsPath)>>"%TEMP%\LocalGroup.vbs"                              @echo.  Wscript.Quit>>"%TEMP%\LocalGroup.vbs"                              @echo.End If>>"%TEMP%\LocalGroup.vbs"                              :doit                              set errlog="%TEMP%\LocalGroup_%RANDOM%.TMP"                              if exist %errlog% del /q %errlog%                              call :quiet>%errlog% 2>&1                              set err=Y                              for /f "Tokens=*" %%x in ('type %errlog%') do (                               for /f "Tokens=2* Delims=:" %%a in ('@echo %%x') do (                               set err=%%b                               @echo !err:~1!                               set err=N                               )                              )                              del /q %errlog%                              endlocal&set %5=%err%                              goto :EOF                              :err1                              @echo Syntax: LocalGroup Computer Group User AorD OK                              endlocal                              goto :EOF                              :err2                              @echo Syntax: LocalGroup Computer Group User AorD OK - AorD %4 invalid.                              endlocal&set %5=N                              goto :EOF                              :quiet                              cscript //nologo "%TEMP%\LocalGroup.vbs" %Comp% %Group% %User% %AorD%