I'm really stuck in Portal...in Test Chamber 18.

Made my way to the main room and got rid of the machines that shoot at you. Now what? Across the room I see two ledges one above the other. I need a cube from the top one...but to get the platform moving I need to push the button in the bottom one, I think.

I've tried creating a portal as high as I can on the wall behind me and another way down on the platform by the water...but when I jump down and through I'm thrown across the room just short of where I want to go.

Help me Obe One Kenobi, your my only hope!

actually the button to move the platform is to the left of you once you enter that room.

Its kinda hard to explain this so you should probably just look on youtube...If i were to try to explain it i would probably confuse you (and myself )