Return value from SQL 2005 SP returns DBNULL - Where am I going wrong?

USE [EBDB]
GO
/****** Object:  StoredProcedure [dbo].[delete_treatment_category]    Script Date: 01/02/2009 15:18:12 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
/*
RETURNS 0 FOR SUCESS
    	1 FOR NO DELETE AS HAS ITEMS
    	2 FOR DELETE ERROR
*/

ALTER PROCEDURE [dbo].[delete_treatment_category]
    (
    @id INT
    )
AS
    SET NOCOUNT ON

    IF EXISTS(
    	SELECT id
    	FROM dbo.treatment_item
    	WHERE category_id = @id
       )
    	BEGIN
    		RETURN 1
    	END
     ELSE
    	BEGIN
    		BEGIN TRY
    			DELETE FROM dbo.treatment_category
    			WHERE id = @id
    		END TRY

    		BEGIN CATCH
    			RETURN 2
    		END CATCH

    		RETURN 0
    	END

Protected Sub dsTreatmentCats_Deleted(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.SqlDataSourceStatusEventArgs) Handles dsTreatmentCats.Deleted
    Select Case CInt(e.Command.Parameters(0).Value)
    Case 0
        'it worked so no action
        lblError.Visible = False
    Case 1
        lblError.Text = "Unable to delete this category because it still has treatments associated with it."
        lblError.Visible = True
    Case 2
        lblError.Text = "Unable to delete this category due to an unexpected error. Please try again later."
        lblError.Visible = True
End Select
End Sub

<asp:SqlDataSource ID="dsTreatmentCats" runat="server"
                    ConnectionString="<%$ ConnectionStrings:EBDB %>"
                    DeleteCommand="delete_treatment_category" DeleteCommandType="StoredProcedure"
                    InsertCommand="add_treatment_category" InsertCommandType="StoredProcedure"
                    SelectCommand="get_treatment_categories" SelectCommandType="StoredProcedure"
                    UpdateCommand="update_treatment_category"
        UpdateCommandType="StoredProcedure" ProviderName="System.Data.SqlClient">
                    <DeleteParameters>
                        <asp:Parameter Direction="ReturnValue" Name="RetVal" Type="Int32" />
                        <asp:Parameter Name="id" Type="Int32" />
                    </DeleteParameters>
                    <UpdateParameters>
                        <asp:Parameter Direction="ReturnValue" Name="RetVal" Type="Int32" />
                        <asp:Parameter Name="id" Type="Int32" />
                        <asp:Parameter Name="name" Type="String" />
                        <asp:Parameter Name="additional_info" Type="String" />
                    </UpdateParameters>
                    <InsertParameters>
                        <asp:Parameter Direction="ReturnValue" Name="RetVal" Type="Int32" />
                        <asp:ControlParameter ControlID="txtCat" Name="name" PropertyName="Text"
                            Type="String" />
                        <asp:ControlParameter ControlID="txtAddInfo" Name="additional_info"
                            PropertyName="Text" Type="String" />
                    </InsertParameters>
                </asp:SqlDataSource>

SqlConnection conn = new SqlConnection(myConnectionString);
 SqlCommand cmd = new SqlCommand(mySqlCommand, conn);

 //     Set up your command and parameters

 cmd.Parameters.Add("@Return", SqlDbType.Int).Direction = ParameterDirection.ReturnValue;

 SqlDataReader reader = cmd.ExecuteReader();
 while (reader.Read())
 {
       //     Read your data
 }

 int resultCount = (int)cmd.Parameters["@Return"].Value;
 conn.Close();
 return resultCount;

SqlConnection conn = new SqlConnection(myConnectionString);
 SqlCommand cmd = new SqlCommand(mySqlCommand, conn);

 //     Set up your command and parameters

 cmd.Parameters.Add("@Return", SqlDbType.Int).Direction = ParameterDirection.ReturnValue;

 SqlDataReader reader = cmd.ExecuteReader();
 while (reader.Read())
 {
       //     Read your data
 }

 conn.Close();
 int resultCount = (int)cmd.Parameters["@Return"].Value;
 return resultCount;

DECLARE @rtn int;
EXEC @rtn = dbo.delete_treatment_category /*insert valid id here > 2*/;
SELECT @rtn;

cmd.CommandType = CommandType.StoredProcedure 'cmd is SqlCommand

Dim retValParam as New SqlParameter("@RETURN_VALUE", SqlDbType.Int)
retValParam.Direction = ParameterDirection.ReturnValue
cmd.Parameters.Add(retValParam)

'add the ID parameter here

'execute

'look at the @RETURN_VALUE parameter here