Extrude Solid up to surface

Hey there,

I want to develop a stair along a curve. The width is limited by two surfaces and the depth is limited by the next step. I set a box in the center of each step. For the depth I set planes where they should end. Know I want to know if there is a solution to extrude the boxes until the surfaces? I just found the operators which work with one vector and evenly. Thanks for your help!