Problems with Executing an External Stored Procedure

I am trying to call an external stored procedure (calls an RPG program). I
keep getting the following error:

"*Exception Details: *IBM.Data.DB2.iSeries.iDB2SQLErrorException: SQL0104
Token @SSN was not valid. Valid tokens: :."

Here is my code:

using (iDB2Connection conn = new iDB2Connection(_CONNSTRING))
{
conn.Open();

string sqlStatement = "MPRLIB.SIGNTIMESHEET (@SSN,
@SIGNATURE, @WORKSTATION, @TOTALHOURS, @COMMENT)";
//string sqlStatement = "MPRLIB.SIGNTIMESHEET (?, ?, ?, ?,
?)";

iDB2Command cmd = conn.CreateCommand();
cmd.CommandType = CommandType.StoredProcedure;
cmd.CommandText = sqlStatement;
cmd.Parameters.Add("@SSN",
timesheet.EmployeeUniqueKey.ToString("0000000000"));
cmd.Parameters.Add("@SIGNATURE",
timesheet.EmployeeTypedName);
cmd.Parameters.Add("@WORKSTATION",
timesheet.EmployeeSignedComputer);
cmd.Parameters.Add("@TOTALHOURS",
GetJobHoursTotal(timesheet.Id).ToString("00000.000").Replace(".", ""));
cmd.Parameters.Add("@COMMENT", timesheet.EmployeeComments);

cmd.ExecuteNonQuery();
conn.Close();
}

I can't seem to figure out what is happening or why I am getting the above
error. My connection string looks like:

private const string _CONNSTRING =
"DataSource=192.168.50.200;DefaultCollection=QMFILES;Naming=sql;UserID=XXX;Password=XXX;";

Could it be a library list issue? The program just references one file that
is in the library list. Any suggestions?

--
Mike Wills
http://mikewills.info
P: (507) 933-0880 | Skype: koldark