how to add fadding effects to display screen

hai to all

I am developing display software. I want to add fading effects to dispaly screen. So can any body help me how to use cuda frame buffer
for below mentioned aplication

i have to initialize the pixel memory of the video frame buffer with starting value. i have to set two frame buffers and fill both with this value - one primay buffer and another one is back buffer…

At the refresh logic rate, i have to reduce the value stored in all memory cells corresponding to all the pixels in the video memory ( subtract by one bit to reduce the intensity by half every time . swap the primary buffer of video memory with back buffer…

/* i have written code roughly */

     #include<stdio.h>
     #define N 768
       main()
       {

          int buffer[N][N]  / / assuming resolution of the screen is 768 x 768 //

          // now i have assigned 255 value to that arry(buffer)//


           memset(buffer, 255, sizeof(buffer)*N*N); //  if we assume like each pixel contains RGB colors so, each byte contains 255 value 

         // now i have to add fading effecting to the my display screen ... so now i am  decrementing   RGB colors for each pixel(768 x 768) from 255 to 15
       

       for(i=0;i<N;i++)
        {
           for(j=0;j<N;j++)
            {
                while( buffer[i][j] > 15)
                 {
                   buffer[i][j] =  buffr[i][j] - 10;

                    Sleep(5000);
                    }
               }
           }

      }

so, i have to do above mentioned like that code using cuda frame(video ) buffer… now i am having NVIDIA 8800GT CARD… if i use this GPU , instead of CPU… can i do all above computation in faster than the CPU… and which version Direct X , i have todownload

thing is i gone through programnig guide 2.0 … but there is no example for cudavideo frame buffer…can any body give some sequentional code for above mentioned porgram…

                               thanking you sir