I found the answer here: https://superuser.com/questions/601015/how-to-update-the-path-user-environment-variable-from-command-line
@echo OFF
for /f "skip=2 tokens=3*" %%a in ('reg query HKCU\Environment /v PATH') do (
if [%%b]==[] (
setx PATH "%%~a;%cd%"
) else (
setx PATH "%%~a %%~b;%cd%"
)
)