How to make a grid cell uneditable without messing up tabbing

[bon_t]

I'm using an AdvancedDataGrid in ActionScript 3/Flex 4. The grid has 5 columns: Caller Intent, Labels, Strategy, Confirmation Mode, and Confirmation Promptlet. All columns are editable except for Labels. However, if you change the Confirmation Mode value to NEVER, the next column Confirmation Promptlet becomes uneditable and is set with the value 'n/a' (this is the desired functionality).

Please refer to the attachment. I changed the Confirmation Mode value to NEVER in the second row. This is what happens when I start tabbing out of the Confirmation Mode cell:
1st Tab: Confirmation Promptlet populated with 'n/a'. I don't see anything in focus.
2nd Tab: The 5th tab from the left in the view stack (dark grey) is in focus.
3rd Tab: I don't see anything in focus.
4th Tab: The button with the green '+' (top left) is in focus. 5th Tab: The grid itself is in focus.
6th Tab: Finally I get to the Caller Intent cell of the next row (when this image was captured)

I tried setting tabEnabled="false" and tabFocusEnabled="false" for the button. I set only tabFocusEnabled="false" for the AdvancedDataGrid. But then the Tab focus starts moving to the components in the upper right panel and lower right panel.

I need to accomplish 2 things:
1. Have tabbing be contained in the grid, in the upper right panel, and in the lower right panel. Meaning tabbing should not cross from one area to another.
2. Have an uneditable field not mess up the normal tabbing behaviour.

Thank you.
Bonnie