Jpegencoder - to CMYK

I’ve got a project where the I need to encode a jpeg in CMYK and I was wondering whether any of you you knew of any means to do this?

I’ve found a cracking script that converts individual rgb ‘points’ to CMYK values but I’m getting stuck when trying to amend the RGB2YUV function in the standard (adobe) jpegEncode – obviously this has to change to allow the four values but should I use another colour profile other than YUV?

  private function RGB2YUV(source:Object, xpos:int, ypos:int, width:int=0, height:int=0):void
        var pos:int = 0;
        for (var y:int = 0; y < 8; y++)
            for (var x:int = 0; x < 8; x++)
                var P:uint = getPixel32(source, xpos+x, ypos+y, width, height);
                var R:Number = Number((P>>16)&0xFF);
                var G:Number = Number((P>> 8)&0xFF);
                var B:Number = Number((P    )&0xFF);
                YDU[pos]=((( 0.29900)*R+( 0.58700)*G+( 0.11400)*B))-128;
                UDU[pos]=(((-0.16874)*R+(-0.33126)*G+( 0.50000)*B));
                VDU[pos]=((( 0.50000)*R+(-0.41869)*G+(-0.08131)*B));

I’ve amended the ‘paramers’ of the jpeg creation so that 8 bits/4 components are specified but have hit a brick wall…

Any help would be fantastic.

Many thanks in advance,