Well, you can use the Scroll Map Event Command to move the camera. Just set it as a paralell process? I think that you are saying that you want it so that the player can move, but the camera is controlled by you, and not the movements of the player? I've never really tried such a thing before, and so I do not know in what way the game determines camera-player position, but one thing you could do is set the transparency Flag on your player, and then teleport him to a place closeby where he is trapped and cannot move. Then you could replace him with an event which looks like him, and you could set up a parallel process which allows the player to control that event, so something like this:
Wait: 2 frames
Conditional Branch: Button [Left] is being pressed
Move Event: [Replacement Hero]
Left
Branch END
Conditional Branch: Button [Up] is being pressed
Move Event: [Replacement Hero]
Up
Branch END
Conditional Branch: Button [Right] is being pressed
Move Event: [Replacement Hero]
Right
Branch END
Conditional Branch: Button [Down] is being pressed
Move Event: [Replacement Hero]
Down
Branch END
Then, when you are finished manipulating the Screen position, just set two variables to the X and the Y-coordinates of that event and Use the Teleport Command to teleport your hero to that position, take away the transparent flag and get rid of the Hero Replacement Event. There is almost certainly an easier way to do this, but I'm tired and cannot think straight. That ought to work. I haven't tested it.