How to launch/close a program when launching/closing another program using the Windows Task Scheduler?

I have a Steam game which I launch in multiple ways such as:

• Clicking the play button on the Steam Library page
• Playing the game in Steam Big Picture Mode
• Manually launching the .exe
• Other batch files

Everytime I launch it, I want to close the process dropbox.exe and everytime I close my game, I want to launch the Dropbox program.

Given that I launch it in many different ways, a batch file to cover all cases is not possible. I have considered using the Windows Task Scheduler to listen to the event when the game's exe launches, but I do not know if this is possible.

So, how do I launch/close a program when launching/closing another program using the Windows Task Scheduler?