Programs are isolated from each other. The CPU makes it so every program thinks it's the only program running and, in 32 bit, has 4 GB of memory all to it's self. So a program cannot affect or monitor another.
So debugging is an exception to the above because computers wouldn't be usable without it and that is built into the CPU/OS.
So run the VB6 program under a debugger, most biz computers have NTSD installed. Note this is not a basic debugger but a machine code debugger.
If it's a window then just wait for the window title. You can use API calls like FindWindow to monitor window titles.
HWND FindWindow( LPCTSTR lpClassName,
LPCTSTR lpWindowName
);