Dear Ying-Shen Yu,
I believe this would work in the case of communication from the embedded IE .NET control to IE itself.

Therefore your code sample:
//PrintCtrl embedded IE object
[DispIdAttribute(0x60020001)]
void MyByteEvent( ref byte[] bytes);

would allow me to do something like this in Javascript (IE):
//PrintCtrl is the id on the <OBJECT> tag
        function PrintCtrl::MyByteEvent( ref byte[] bytes)
           {   //setting value to html element via javascript DOM            
               document.all.myForm.bytes.value = bytes;
           }

That is fine, but I need to pass a byte[][] from code-behind (aspx.cs) to the embedded I.E. control, which would be the reverse (opposite) of the above sample.

Do you know how this can be accomplished ?

Thanks in advance.