Texturing Terrain

I don''t know if this has been asked before, if so I apologize right away. I''m currently into terrain-rendering, and of course I use height maps to create my terrain. Now the texturing is a problem to me; The texture I map onto a quad depends on the height of the Quad. But if one quad stretches from the deepest point of the mesh to the highest It would be cool to have the lower two vertice have a sand texture and the upper two a stone texture. This has been done in games before, so there must be some way, but I just can''t figure it out. The only method I could think of (which I think is a horrible solution) is to draw the quad with a stone texture, then draw a quad with the sand texture + total transparency on the upper two vertice. Does anybody here have a simple solution in idiomatic C++? Thnx in advance! SNAFU - Sitation normal; All fucked up