Are you trying to format the whole TOC, or just one line?
For the whole TOC, you're normally better off editing the styles.
If you click in the TOC and use the arrow keys to move through, you can
find places where the TOC1, TOC3 styles are shown (rather than
'Hyperlink) in Word's Formatting toolbar.
Then you can click the Styles and Formatting icon (or Format Styles
and Formatting...) to edit the style.
You may want to turn "auto-update" OFF for those styles, too...
cheers
Jay