I want to show calls,meeting and tasks of each opportunity related with account module
You don't need to create a relationship, I believe there already is a relationship between Accounts and Opportunities and one between Opportunities and each of the Calls/Meetings/Tasks modules. What you need is a way to display that information on the Account.
To do that, consider using a dashlet in the intelligence pane to display the calls/meetings/tasks related to each Opportunity.
With a little searching you can find examples of custom dashlets on the Developer Blog, for example a basic one:
Thanks for this answer, but I'm concerned this may go beyond having a dashlet. I want to make sure that the note/meeting/task is directly related to all 3 modules (contact/account/opportunity) so that users can see it in every instance.
For example, let's say I want to attach a note to Joe Smith at ABC Company that is related to an opportunity called "ABC Software Sale." I need to make sure: 1. If a user is pulls up Joe Smith (a contact), that user should be able to read my note. 2. If a different user is reading about ABC Company (an account), this user should also be able to see the note on the account page.3. If my boss is reviewing the ABC Software Sale (an opportunity), my boss should be able to see my note related on the opp page.
How would having a custom dashlet in the intelligence pane solve the problem?
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