How do I use the control pad while holding a button to make a platform move?

LoungeGames

In my game, there are new types of platforms in each world which you must go across to reach the goal. In my next world, there is a platform where you land on it, and when you hold down the B button, it goes in the direction that you move the control pad with. I have tried this, and the platform does not move. I need to know how I could make it move, and have it move without moving the character, but make the character move again when the B button is released. I also need a way to test this on my computer so I know it is working, and can test the levels.