I’m the author of that blogpost (thanks muchly for posting that link here flamerz). The rrun (emeditor macro) script allows you to run only selected lines as well, though the version available will (as you say) run rterm each time.
I have modified the script, so that if a flag called “useSource” is set true, and you have a running instance of RGui + R Console (default when rgui is launched from shortcut), it will run the code in that instance and not reload rterm each time. I found it was more reliable to use the “source” command, rather than sending strings to the REPL;
echo and keep.source args are hardcoded in the script, but of course feel free to modify that! in r, if you are not already familiar with this command, try “help(source)” for more options.
I’ll upload the script and do a little blog post about it to explain it more.