Thank you, your're very kind.
You understood perfectly what I was trying to ask.

Anyway, I already considered that solution. But there's a big problem.

Speed movement here is not framerate based (I don't use a fixed frame rate and move the sprites each frame at a fixed speed).
I use speed based on how fast the frames are beeing rendered. If at a certain point the framerate drops, the speed per frame raises, and the other way round. this way, the objects move always at the same speed independent of the FPS and the CPU.

And here is the problem.
If I do what you say, in a certain point, imagine I'm about to land on a platform (5 pixels above), the movement for that frame could be bigger (imagine the FPS drops), so the sprite falls 10 pixels that frame (imagine), and passes by the ground, so it does not collide with its feet on the platform.

I don't know If I explained myself clearly.. (hope so)