GetWindowTextW with Pointers

Hy,

i've not understand, how to use jawin with pointers.
The GetWindowText(Win32 API) funktion needs at "LPTSTR lpString" a pointer
to string buffer (returns the name of the window in this string).I've tried
some possiblities with no solution. Always getting a Exception.
I'm not clear enough about the syntax of the instruction string, too.

findWin2 = new FuncPtr("USER32.DLL", "GetWindowTextW");
NakedByteStream nbs = new NakedByteStream();
LittleEndianOutputStream leos = new LittleEndianOutputStream(nbs);
leos.writeInt(whnd);
leos.writeInt(255);
res=findWin2.invoke("Ip4I:I:G",12,nbs,new Object
[255],ReturnFlags.CHECK_FALSE);


-->THE WIN32 API DEFINITION
int GetWindowText(
    HWND hWnd,
    LPTSTR lpString,
    int nMaxCount
);

Maybe someone has an idea, cause after several hours i gived up :-(