Calling DLL inside dynamics ax 2009

Hi All,

    Just want to seek help/advice regarding  calling DLL file inside AX 2009. I tried creating DLL using c#  in .NET Framework 3.5 with Singing details and public    token. I also generate the public token for this DLL using sn command in command prompt. Then I copy the DLL in the bin folder of AX 2009 Client with other standard DLL file like business connector, I registered it in GAC using commands gacutil. Then I tried accessing the custom DLL file in AOT > References but  AX 2009 prompt me an error "INVALID OBJECT NAME". What is this mean?. Another question, why the standard Sharepoint DLL file can't access in AOT> References?

Can anyone give me a step by step process for calling DLL inside AX 2009?

Thanks in Advance. Appreciate every answer.