Complex Situation with MessageWindow Handle

I have an exe written in C# managed code .NET CF and pass the MessageWindow
handle to a win32 dll written in evc++. Once I get the handle I send that
handle to a win32 exe written in evc++ using IPC (WM_COPYDATA) mechanism. Now
I have the MessageWindow handle from .NET CF exe into my evc++ application.
But when I start sending a data to .NET CF application, it received my
message, but the data was empty. When I do the same from the dll where it
received the handle works fine. I don't know why it did not pass the data
from my application. Am I missing anything? Please share your information.

Thanks,
GK