Here's the code from Appmon+ that sets the current media message. Looks like it came from the Now Playing script
code:
// Function by -dt-
function setNowPlaying(enabled, type, format, title, artist, album, contentID){
if(typeof(type) == "undefined")type = "Music";
if(typeof(format) == "undefined")format = "";
if(typeof(title) == "undefined")title = "";
if(typeof(artist) == "undefined")artist = "";
if(typeof(album) == "undefined")album = "";
if(typeof(contentID) == "undefined")contentID = "";
enabled = Math.abs(enabled);
var WM_COPYDATA = 0x4A;
//reference
var song = Interop.Allocate(512);
//change the Music thing to Games or Office or
song.WriteString(0, "\\0" + type + "\\0" + enabled + "\\0" + format +"\\0" + title +"\\0" + artist + "\\0" + album + "\\0" + contentID + "\\0");
//write our copyDataStruct Structure
var copyDataStruct = Interop.Allocate(12);
copyDataStruct.WriteDWORD(0, 0x547); //dwData
copyDataStruct.WriteDWORD(4, song.Size); //cbData
copyDataStruct.WriteDWORD(8, song.DataPtr); //lpData
//Send it to all open messengers
var hMSGRUI = 0;
do{
hMSGRUI = Interop.Call("User32", "FindWindowExW", 0, hMSGRUI, "MsnMsgrUIManager", 0);
if(hMSGRUI > 0){
Interop.Call("User32", "SendMessageW", hMSGRUI, WM_COPYDATA, 0, copyDataStruct);
}
}while(hMSGRUI != 0);
}