The size of a text box in Access doesn't have anything to do with text on a Word doc.  I'm assuming you are merging it.

The only way that I'm aware of is to limit the number of characters in your text field in the Access database or to allow more room in the merged document.
It's been a while but I don't think you have a can grow / can shrink in Word.
Another alternative would be to make a report out of your document and do away with Word altogether.

Thanks, Scott.
My current solution uses a character count but that does not take into account carriage returns. These make the text take more lines in the box.