is it possible to state somehow that "keyboard_state(DIK_LEFT)" will not be possible after a boundary test?

If your against a boundry, and the user wants to keep moving over, ignore them. Or give them a warning sound ''BEEP''.

Is this what you mean?

okay, i explain a bit more...
i am trying to test/check boundaries with the bobs. If a certain bob hit the boundary,
it will not cross it.

but the problem is that, i am moving all 4 bobs
(tetris) at the same time..

so how do i maintain each bob so that they stay
in their respective positions and not overlap
one another?