Hi! :) 

Everytime when I try to edit/change PricebookEntry field on Work Order Line Item by adding different product I get the error message.

I checked and the field is standard, with lookup to Price Book Entry. The editing is enable, and field accesible is also set as editing for each profile. 

Do you have any ideas?:) 

Hello everyone,
I have a requirement that
1.Attendees can self register woth their name ,email and they can express interest in specific area for corporate seminar(picklist values).
2.attendees are informed by email on upcoming corporate seminar for their area of interest.
3.corporate seminar management team(users) will confirm attendees registration after they receive payment.
Here attendees and corporate seminar management team are the users. 
I am practicing this project and i am not getting the idea how to proceed further in this steps.Can anyone please guide me.