Change text box values as tab through datasheet

I've got a form with a subform and three text boxes on it.

The subform is a datasheet view of the query that is the form and the
subform's record source. This subform works perfectly. My problem is with
the three text boxes.

What I want to happen is this: as I tab forward and backward through the
cells of the datasheet, I want the values of the text boxes to change
according to which cell I'm in.

How?

The fields of the datasheet view are as follows:
Category
English
Spanish
Portuguese
Kreyol
French

It's simply a five language dictionary. The category field is for stuff like
parts of speech, months, etc.

The three text boxes are as follows:
Synomyms
Antonyms
Example

Here's the idea again. As I tab through the dictionary, I want the values of
the text boxes to change according to the word (cell) that has focus, that
is, I want the "Synonyms" text box to display synonyms of the word I select
in the dictionary. Ditto for the "Antonyms" text box and also for the
"Example" text box.

I've got the little database zipped up and ready to send. It has only two
records in it so far.

Thanks!
-Dave