CMD/batch are going to be deprecated in the future you're better off using powershell.
If you're using a script to install the software you could do
Code:
install sofware....
:LOOP
IF EXIST PATHTODROPBOXDIRECTORY\reboot.bat (
shutdown /r /t 10 /c "Computer restarting to complete software install"
GOTO EXITLOOP
) ELSE (
TIMEOUT /T 300
GOTO :LOOP
)
:EXITLOOP
exit 0