制表位不适用于数据模板中的文本框

I'm writing a really simple name / value editor control where the value is editable - label on left and property text box on right. Control works fine except that when the user hits TAB when inside one of the "value" text boxes on the right, the focus shifts away from my control to the next control in the hiearchy. I want the focus to go to the next text box in my control so users can just tab between property text boxes. I tried setting "IsTabStop" to true but doesn't seem to work.I'm writing a really simple name / value editor