I assume that you are on the B2F.
Ice Path B2F
Wild Levels: 22 - 24
Same Pokemon, different levels. Go a bit up and slide to the left so that you
hit the boulder. Then, slide up, left, down, left and pick up the MAX POTION
situated here. Then, slide down, right, down, right, up and go around so that
you slide into the boulder again.
Now, slide down, left, up, right to reach the center land. Pick up the FULL
HEAL, then go down the ladder.
(By the way, there is a hidden CARBOS if you examine the wall between the rock
and the tile of jutting wall in the bottom right corner.)
(Taken from GameFaq Walkthrough)