Moving Object's Collider High during Animation

Hello Guys! I'm new to the Unity, and i've just completed that official Mecanim tutorial, and now i have a problem. I'm using the Free version of Unity, so I can't use curves during Animations

I made that when the players aproacehs a cube, climbs it, and then the movement continues from there, but my problem is, that I cant change the collider High during this animation. I think that its possible to do this without curves, using other object as a colider for the Player or something like that... Can someone help me?

In the picture, it shows what i mean, i want to make the colider High goes up when the Player is climbing, instead of sitting there, like in the picture (sorry for the bad english )