You can add / create windows registry key through command line by using REG.Exe tool.
Example:
Reg Add HKLM\Software\Classes\Excel.Sheet.8\ /v Browserflags /t REG_DWORD /d "8" /f
/v value name to add, under the selected Key
/t RegKey data types:
[ REG_SZ, REG_MULTI_SZ, REG_DWORD_BIG_ENDIAN, REG_DWORD, REG_BINARY, REG_DWORD_LITTLE_ENDIAN, REG_NONE, REG_EXPAND_SZ ] If omitted, REG_SZ is assumed
/d data to assign to the registry ValueName being added
/f force overwriting the existing registry entry without prompt
