Hello
You can use the control's TabIndex property.
Like TabIndex="0" (number from low to high).
You may also set the IsTabStop property to "True" or "False" wether you like the control to be included in the tab loop or not.
<textbox text="tabbed" istabstop="True" tabindex="0" />
<textbox text="Tabbed" istabstop="True" tabindex="1" />
<textbox text="Skipped" istabstop="False" />
<button content="Done" istabstop="True" tabindex="2" />
Hope it helps!