You can do formatting to individual words ONLY if you have Office 2007 and above (or use something like Stephen Lebans code for previous versions). For 2007 and above you can set the field in the table to be MEMO and then you change the TextType from Plain Text to Rich Text. And then make sure the text box you have on your form is changed from Plain Text to Rich Text.
Then you can do basically the same formatting you would be able to do in Word, Excel, etc.