Global to Local Mouse Cordinates

in my Controller Class:

stage.addEventListener(MouseEvent.MOUSE_MOVE, mouseMoveListener);

//for snapping my object to a grid

//im using this algorithm

protected function mouseMoveListener(e:MouseEvent):void {
            brick.x = mouseX - mouseX%theGrid.getGridSize();
            brick.y = mouseY - mouseY%theGrid.getGridSize();
}

brick it's inside a container and its position in x axis is 200px

When the brick is moving, the x and y value are based on stage x and y mouse.

The 0 in the stage should correspond to -200 inside my container.

How can i use globalToLocal method?

instead write:

brick.x = (mouseX - mouseX%theGrid.getGridSize())-200;

?

thanks