How can i pass NULL value in Store Procedure?

Hi guys,
I am calling one store procedure from MS SQL Server 200, i had create the follow layout:
But i need pass to MSQL SEVER the CPF = NULL, when i execute the procedre the CPF send empty value (not null).
I already changed Communication Channel parammeter "Interpretation of Empty String Values" to "Null Value" value.
But the interface always send empty string instead of null.
How can anybody help me, please?
Edited by: João Noberto dos Santos Junior on Jun 24, 2009 5:00 PM

To achieve this through "Interpretation of Empty String Value" in the cc, you will have to implement a patch which is sent to you by SAP when an OSS is raised. By default its not available, i mean you can configure it but it will actually not work.
As a temporary solution you can map your element with a constant/mapwithdefault field with value mentioned as NULL.