Call store procedure & Get Value from Store Procedure

Call store procedure & Get Value from Store Procedure
I can't get value from function return in package.I use script in example dot net but I can't get retvalue.If I call Function CountAuthors() in sqlplus (Oracle DB) I can get value, why I can't?

Example.
Dim cntAffectedRecords As Integer
OleDbcommand1.CommandText = "CountAuthors"
OleDbCommand1.CommandType = CommandType.StoredProcedure
OleDbConnection1.Open()
OleDbCommand1.ExecuteNonQuery()
OleDbConnection1.Close()
cntAffectedRecords = CType(OleDbCommand1.Parameters("retvalue").Value, Integer)
MessageBox.Show("Affected records = " & cntAffectedRecords.ToString)

Please tell me..:-) thank you for all answer.