LDAP Vs ADSI Parameter Problem

Dear friens,
I'm having a problem with ADSI and SQL... Could you tell me, where is the error? The problem surge when I try to use parameter€¦

"
CREATE PROCEDURE TEST
AS
DECLARE @charVariable nvarchar(11);
DECLARE @SQLString NVARCHAR(500);
DECLARE @ParmDefinition NVARCHAR(500);

/* Build the SQL string one time. */
SET @SQLString = N'SELECT * FROM OPENQUERY(ADSI,''SELECT * FROM ''''LDAP://DC=GrupoCGD,DC=com'''' WHERE objectClass = ''''user'''' AND sAMAccountName=@UserID'')'

/* Specify the parameter format one time. */
SET @ParmDefinition = N'@UserID varchar(11)';

/* Execute the string with the first parameter value. */
SET @charVariable = 'rhs0002';
EXECUTE sp_executesql @SQLString, @ParmDefinition,
@userID = @charVariable;
"

ERROR is:
Msg 7321, Level 16, State 2, Line 1
An error occurred while preparing the query "SELECT * FROM 'LDAP://DC=GrupoCGD,DC=com' WHERE objectClass = 'user' AND sAMAccountName=@UserID" for execution against OLE DB provider "ADSDSOObject" for linked server "ADSI".


FOR EXAMPLE THIS VIEW WORKS€¦
USE [dbGestaoDesktop]
GO
/****** Object: View [dbo].[AD_VW_DIR_Users] Script Date: 11/22/2006 11:53:13 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE VIEW [dbo].[AD_VW_DIR_Users]
AS
SELECT TOP (100) PERCENT cn, createTimeStamp,department, extensionAttribute1
FROM OPENQUERY(ADSI, '
SELECT createTimeStamp,cn, department, extensionAttribute1
FROM ''LDAP://OU=DSO,OU=Utilizadores,OU=Servicos-Centrais,OU=cgd,DC=GrupoCGD,DC=com''

WHERE objectclass=''user''


')
AS MyTable
WHERE (NOT (cn IS NULL))
ORDER BY createTimeStamp

THANKS