struct SECTION
{
     float top,bottom,left,right;
};

SECTION newSect()
{
     SECTION newSection;

     newSection.top = -0.7 + ( (rand() % 400) / 1000 );
     // should generate a random number from -0.7 to -0.3

     // code is continued for bottom, left, and right...

     return (newSection);
}

// Later, in the main game loop...

SECTION tunnel_section = newSect();
printf("%f",tunnel_section.top);