Put your two icons next to each other on your desktop - The icon to launch Bioshock, and the icon to launch the trainer.
Make sure you don't have the trainer open to start with.
Double click the icon to launch Bioshock first. Wait for the Steam popup to come on screen.
As soon as the Steam popup go away, a very small Bioshock label/image will popup in the middle of your screen as the game starts to load. As soon as this happens, double click to launch the Trainer.
The goal is to launch the trainer AFTER the Steam stuff, but before the game actually fully loads and takes over your screen. If you did this correctly the trainer should work perfectly fine for you. Good luck!
i tried both. running it as you say the normal way.
and after the game was loaded.
i press buttons and nothing happens i check the trainer still says game is loading.
I'm going back and playing some old games using trainers and after wasting so much time trying to get Alt-Tab/Enter to work ,with no luck whatsoever, I read your post and got it working immediately.
Doing it your way started up the game with a black screen, however, but all I did was click the screen and the menu shows up as normal. What I think happens is that the game is set to the background when you start the trainer and clicking the screen moves it to the foreground.
Anyway, thanks again!