Associate an 'event' content type with a 'project' content type
First of all i totally agree with Molot's comment. 

Just to help i will provide my opinion on how to do this:

Use the Node reference url widget module in combination with the Field Permissions module. With the 1st you can create an "Add an Event" link for every Project node and set the fallback behaviour of the field as autocomplete and with the 2nd you can set the permissions for that node reference field.