Assignee, Reporter, Request type, and more) in a request type, you can also add custom fields.One of these custom field types is Cascading fields.You can use these to create conditional fields with two lists: a parent list of values and a child list of values dependent on what is selected in the parent list.
Make use of the Where I am: field if you are interested in filtering messages sent to you. Use the fields available to you in the Filter dialog box to configure your rule's conditions. Type a name for your rule in the Name: field, and then click Condition.