How to use views achieve this I've two nodes Person and Mission. A Mission can contain many Person's. Now if I'm browsing Person node, then in right side bar block I want to show all Mission's associated with this Person.

Example:

Mission1 contains ( 1 field containing multiple values):


Person-A
Person-B


Now if I go and view Person-A then in a block I should see Mission1 as it is associated with it.
You can use a CCK "node-reference" field. This way you can "link" one mission page on all person pages. After you did this you can easily make a view that gets all persons that are in the mission node...

Maybe you can take a look at:
http://drupal.org/project/Relation