how to change the next GIF image in windows phone 7

Hi friends, I am doing snakes and ladder game in windows phone7, i need to change gif images according to dice fall when i click the button continuously , i have given dice image in gif format and i have button to generate the random dice, how to change the Gif image according to random dice pls tell me if any body known ,my code is

Dice_Rolling(){

   randomdice = ra.Next(1,6);if(randomdice ==1){ImageTools.IO.Decoders.AddDecoder<GifDecoder>();ImageSource=newUri("Images/Gif/dice_anim_1.gif",UriKind.RelativeOrAbsolute);this.DataContext=this;}if(randomdice ==2){ImageTools.IO.Decoders.AddDecoder<GifDecoder>();ImageSource=newUri("Images/Gif/dice_anim_2.gif",UriKind.RelativeOrAbsolute);this.DataContext=this;}if(randomdice ==3){ImageTools.IO.Decoders.AddDecoder<GifDecoder>();ImageSource=newUri("Images/Gif/dice_anim_3.gif",UriKind.RelativeOrAbsolute);this.DataContext=this;}}publicUriImageSource{ get;set;}privatevoid button1_Click(object sender,RoutedEventArgs e){Dice_Rolling();}