set T_tempDir on Windows

Hello Guys

I'm not a developper and i need only to help a collegue to make RFGUI run. It's installed in the user profile but we need to change the path of the R_TempDIR outside of the profile.

I tried creating a Renviron.site under ..../etc/ with the following:

TEMPDIR=C:/rtemp
TMP=C:/rtemp
TEMP=C:/rtemp

but nothing....how can i do it?