How to referesh one view UI from other view UI

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Silverlight4

MVVM

PRISM

I have two Views called UserView and RoleView.

UserView.xaml contains RadGridView which contain three columns
UserID (Label) | UserName (Label)| Role (Dropdown).

RoleView.xaml contains one TextBox where i can add Roles into database.
Role (Textbox).

Step 1. Now first i open the UserView.xaml and it will display records from database with appropriate roles.
Step 2. Now i open new page RoleView.xaml (minimize UserView.xaml).
Step 3. I have added one role. (AdminRole)
Step 4. Now i open UserView.xaml (it is already in memory, so just i navigate to this page)

Step 5. Now i double click to any of the row with Role (Dropdown column) it will comes into edit mode and populate list of roles.

but it will not display recently added role (AdminRole) in dropdown. because of the data source will not getting refresh.

If i am closing the UserView.xaml and reopen this page then it will display recently added role (AdminRole) in dropdown.

Note: my requirement is like, i have to update or notify all opened views once any of the change from anywhere.

I am using Silverlight 4 (MVVM) PRISM telerik RadGridView

Your help/comment/suggestion would be highly appreciated!

Thanks,
Imdadhusen