How can I read characters from the screen?

[hanness]

Assume that I am initializing my display like this:

        _FullScreen _Off , _Smooth
        _FreeImage oldimage&
        Font& = _LoadFont(FontPath$, FontSize, "MONOSPACE")
        _Font Font&

Now I write a bunch of text to the screen.

Later, I want to read the character at the upper left of the screen. I tried to do this like this:

print screen(1,1)

or

MyVar$ = CHR$(screen(1,1))

However, I'm getting an illegal function call when the line with screen(1,1) is executed.

Is this only valid with screen mode 0 or am I missing something here?

If this cannot be made to work, is there any other way to read characters from the screen?