How to debug a program spawned by another program?

[jonwil]

Its for the Origin digital software store.
Origin.exe (main store program) runs. When you click "play" it starts OriginClientService.exe. This then starts the actual game exe (lets say RenegadeLauncher.exe for one of the exes I am working with). When RenegadeLauncher.exe runs, some unknown form of inter-process-communication is done between Origin.exe/OriginClientService.exe and RenegadeLauncher.exe to verify that its genuine and authorized and if it is, RenegadeLauncher.exe runs and does its work. If you run RenegadeLauncher.exe directly, it doesn't recieve whatever "this is legit" instructions it is looking for and instead of running, it starts Origin if needed, passes Origin a "play this game" instruction and then terminates (whereupon Origin starts the game as above)

The CREATE_SUSPENDED idea wont work because OriginClientService.exe does not use CreateProcess, it uses ShellExecuteEx.