Thank you very much for your reply.

My purpose is to extract all opportunities and line items from an xls file which is generated by another system, and then upload those opportunities and their lineitems to the salesforce.com through salesforce APIs.

I first get all opportunities and instantiate all those Opportunity objects, then I upload those objects. I succeed and can get generated opportunity IDs.

Second, I instantiate OpportunityLineItem objects that belong to the specific Opportunity object, and assign those line item objects the generated opportunity ID, and upload them, again, I succeed and can get all OpportunityLineItem IDs.

Third, after I succeed with uploading all OpportunityLineItem objects belong to all Opportunity objects, I begin to instantiate OpportunityLineItemSchedule objects, and assign them OpportunityLineItemId property, then I upload OpportunityLineItemSchedule objects belong to different opportunities respectively. I fail, and get the error "insufficient access rights on cross-reference id". I set relatively few properties to the OpportunityLineItemSchedule objects, following is my code snipet:

schedule.Description = description;
schedule.ScheduleDate = DateTime.Now.AddDays(1);
schedule.ScheduleDateSpecified = true;
schedule.Type = "Quantity";

schedule.OpportunityLineItemid = opportunity.Id;

Does this make sense?

I made a mistake in the last post, the last line of code should be:

schedule.OpportunityLineItemId = lineItem.Id;

it is the Id of an OpportunityLineItem, not an Opportunity, that has been set to schedule.OpportunityLineItemId.