How do you retrieve the Data Extension object structure using AMPScript?

I almost have it, but need some help translating into AMPScript how to get the SendableDataExtensionField.Name, SendableSubscriberField.Name and Template.CustomerKey when retrieving the DE object structure. Below is the code I currently have:

%%[/* ==================================== *//* Retrieve Data Extension *//* ==================================== */SET @rrDE = CreateObject("RetrieveRequest")SetObjectProperty(@rrDE, "ObjectType", "DataExtension")AddObjectArrayItem(@rrDE,"Properties","Name")AddObjectArrayItem(@rrDE,"Properties","ObjectID")AddObjectArrayItem(@rrDE,"Properties","CustomerKey")AddObjectArrayItem(@rrDE,"Properties","PartnerKey")AddObjectArrayItem(@rrDE,"Properties","Description")AddObjectArrayItem(@rrDE,"Properties","IsSendable")AddObjectArrayItem(@rrDE,"Properties","IsTestable")AddObjectArrayItem(@rrDE,"Properties","CategoryID")AddObjectArrayItem(@rrDE,"Properties","Status")AddObjectArrayItem(@rrDE,"Properties","IsPlatformObject")AddObjectArrayItem(@rrDE,"Properties","DataRetentionPeriodLength")AddObjectArrayItem(@rrDE,"Properties","DataRetentionPeriodUnitOfMeasure")AddObjectArrayItem(@rrDE,"Properties","RowBasedRetention")AddObjectArrayItem(@rrDE,"Properties","ResetRetentionPeriodOnImport")AddObjectArrayItem(@rrDE,"Properties","DeleteAtEndOfRetentionPeriod")AddObjectArrayItem(@rrDE,"Properties","RetainUntil")AddObjectArrayItem(@rrDE,"Properties","Template.CustomerKey")AddObjectArrayItem(@rrDE,"Properties","SendableSubscriberField.Name")AddObjectArrayItem(@rrDE,"Properties","SendableDataExtensionField.Name")/* AddObjectArrayItem(@rrDE,"Properties","DataRetentionPeriod") << THIS DOES NOT WORK */ SET @sf1 = CreateObject("SimpleFilterPart")SetObjectProperty(@sf1, "Property", "CustomerKey")SetObjectProperty(@sf1, "SimpleOperator", "equals")AddObjectArrayItem(@sf1, "Value", "SAMPLE_DE_CUSTOMER_KEY")SetObjectProperty(@rrDE, "Filter", @sf1)/* Execute the Retrieve */SET @rr = InvokeRetrieve(@rrDE)set @cnt = RowCount(@rr)FOR @i = 1 to @cnt DO    SET @curRow = Row(@rr, @i)    SET @objID = Field(@curRow,"ObjectID")    SET @CustomerKey = Field(@curRow,"CustomerKey")    SET @Name = Field(@curRow,"Name")    SET @PartnerKey = Field(@curRow,"PartnerKey")    SET @Description = Field(@curRow,"Description")    SET @IsSendable = Field(@curRow,"IsSendable")    SET @IsTestable = Field(@curRow,"IsTestable")    SET @CategoryID = Field(@curRow,"CategoryID")    SET @Status = Field(@curRow,"Status")    SET @IsPlatformObject = Field(@curRow,"IsPlatformObject")    SET @DataRetentionPeriodLength = Field(@curRow,"DataRetentionPeriodLength")    SET @DataRetentionPeriodUnitOfMeasure = Field(@curRow,"DataRetentionPeriodUnitOfMeasure")    SET @RowBasedRetention = Field(@curRow,"RowBasedRetention")    SET @ResetRetentionPeriodOnImport = Field(@curRow,"ResetRetentionPeriodOnImport")    SET @DeleteAtEndOfRetentionPeriod = Field(@curRow,"DeleteAtEndOfRetentionPeriod")    SET @RetainUntil = Field(@curRow,"RetainUntil")    if @IsSendable == "True" then        /* ============================================================== */        /* THIS PORTION IS WHERE I NEED HELP getting the following information  */        /* ============================================================== */        SET @SendableDataExtensionField = Field(@curRow,"SendableDataExtensionField")        SET @SendableSubscriberField = Field(@curRow,"SendableSubscriberField")        SET @Template = Field(@curRow,"Template")        /* ============================================================== */        /* ============================================================== */    endifNEXT @i]%%