plsql and vb

[dreams]

Hi every one,
I don't know how to retrieve the result from plsql into vb :(
my plsql function is:

create or replace function log_in (name in int)
return int
is
x int;
begin
x :=1;
return x;
end log_in;

my vb.net code is:
con.ConnectionS tring = "Driver={Micros oft ODBC for Oracle};Server= localhost;Uid=h r;Pwd=hr"
Dim sql As String = "declare y1 int ;begin y1 := log_in(2); end;"
Dim cmd As New Odbc.OdbcComman d(sql, con)
cmd.CommandType = CommandType.Sto redProcedure
con.Open()
Dim rv As OdbcParameter
rv = cmd.CreateParam eter()
rv.Direction = ParameterDirect ion.ReturnValue
rv.DbType = DbType.Int16
cmd.Parameters. Add(rv)
Dim ret As Integer = cmd.ExecuteScal ar()
MsgBox(ret)
con.close()

the output is always 0 instead of 1 !!!
could any one help me :)