Firing a Tab stroke after CTRL + V on a WPF Textbox?

Hi there,

After paste a text (CTRL + V) I would need the cursor would move onwards to the next TextBox without user interaction.

It's an entry form where you must fill 5 TextBoxes which composed the full Activation Key of my application.

LostFocus and LostKeyBoardFocus are not useful here.

Moreover, I would need that whether the user paste less digits the action does not fire (only if all the digits has been entered)

Thanks a lot

Primary platform is Windows 7 Ultimate 64 bit along with VS 2012/Sql2k8 for WPF/SilverLight projects.