Change the focus of button,capture enter key from scanner

 In the below snapshot,the user clicks on scan,and below popup appears(grid with two columns item,barcode)..

The User uses barcode scanner...When the user finishes scanning last item i.e 2nd item (in this case) the OK button must be focused/invoked when user just presses enter.

after ok is pressed the control has to go to main page with focus on execute.I have set the focus in code for execute button but still  there is problem in focus

<DataTrigger Binding="{Binding FocusExecuteButton}" Value="True"><Setter Property="FocusManager.FocusedElement" Value="{Binding ElementName=btnExecute}"/></DataTrigger>

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