Someone

    vector currentPos = llGetPos();

    vector relative_pos = (targetPos - currentPos) / 25.0;
    float max_ground = -1.0;
    float ground;
    vector foo = currentPos;
    integer x;
    for(x=0;x<=25;++x)
    {
        ground = llGround(currentPos + (relative_pos * x));
        if(ground > max_ground)
        {
            max_ground = ground;
        }
    }