How do I... Every X pixels..

Start of layout
    Sprite.OldX = Sprite.X
    Sprite.OldY = Sprite.Y

Compare two values: distance(Sprite.X, Sprite.Y, Sprite.OldX, Sprite.OldY) >= X
    Do something
    Sprite.OldX = Sprite.X
    Sprite.OldY = Sprite.Y[/code:2t5n08eg]

Start of frame 
    -> Set player.oldPos to player.currentPos

Every tick 
    -> Add to Player.movementDelta : distance(player.oldPos, player.currentPos)
    -> Set player.oldPos to player.currentPos

While player.movementDelta >= 32
    -> Do what you want here
    -> Substract 32 to player.movementDelta[/code:3160nrp1]

ninja'ed ! You should use definitely use a while if you plan of having tremendous speed, otherwise don't bother.