I got it!
For anyone else who might want to perform registry edits in the HKCU area, here it is:
delete __appendfile
appendfile {concatenation "%0d%0a" of ("reg add %22HKEY_USERS\" & it & "\SOFTWARE\Microsoft\Internet Explorer\Main%22 /v %22SpellChecking%22 /t REG_DWORD /d 00000000 /f") of names of keys of key "HKEY_USERS" of registry}
delete delreg.bat
move __appendfile delreg.bat
waithidden delreg.bat
Thanks to all those who replied!