yes.
Maybe you have to implement something like signalisation about all your projects completed. May be it would be a shared list with reports from all projects you launched with statuses. The separate project would act as a watcher of list and should be run finalization script (hibernate, sleep, poweroff)
How to implement finalization, read this. http://stackoverflow.com/questions/6351861/how-to-initiate-standby-sleep-from-command-lineA
I think, lokiys's method is much more simple. You have only to write batch script
@echo off
setlocal enableextensions
set myprocess=base.exe
:begin
for /F %%x in ('tasklist /NH /FI "IMAGENAME eq %myprocess%"') do if %%x == %myprocess% goto found
echo not running
ping -n 5 127.0.0.1 > nul
rundll32.exe powrprof.dll,SetSuspendState 0,1,0
goto end
:found
echo running
ping 127.0.0.1 -n 11 > nul
goto begin
:end
but the worst thing is that no projects are working but the base.exe instanse is still running.