Yeah. I'm truly sorry if you think we're acting like you're stupid, but we we just need more details about exactly what you're doing. Did you define video_screen like this:

video_screen = 1;

OR like this (the correct way)?:

// outside of any functions!! at the beginning of the script
var video_screen = 1;

For checking this, use TAB in the engine and type video_switch(0,0,1);.