Detecting Selected Item

There is no way to tell what item is selected in "B".

I think the best you're going to get is to have Link use the item (press B once) and then the item becomes active until B is pressed again. That way, if any other item is used, the shield goes away.

I would do it like this

bool flag = false;
item script shield{
void run()
{
	flag = !flag;
}
}
ffc script do_shield{
void run()
{
	while(true)
	{
		if(flag)
		{
			// activate shield
			if(Link->InputB)
			{
				flag = false;
				// deactivate shield;
			}
		}
		Waitframe();
	}
}
}

Doesn't it detect whether you hold down the button too?

Well, either way, this is a pretty decent start to getting it consistant with Gameboy style Zeldas

Yes I think that option will work for my quest, all I have to do is make it take MP while in use, this way it works like a switch. I have not tested the script yet but it looks good, just one question what exactly does this line do?

flag = !flag;

it looks like it would set bool flag to false.. mabye 😕

thanks for the script and the idea, I am going to do a similar thing with my 'Elven Armor' item, when activated acts as a red ring and takes MP when not activated acts as a blue ring..

It just flips the value in flag. ! is the "not" operator. So, if flag is true, then !flag (not flag = not true) == false.

Right, the long way of doing it is

if(flag == true) flag = false;
else flag = true;

Can global variables be accessed on any screen?

Yes, by any script.