Word and VB.net

I was wondering if there was a way to replace the text in a word file with the text in a textbox from vb. I know you can open up word and enter a <bookmark>. But I want to know if I can replace the text that is already there.

You can use Word's Find & Replace functionality through VB. Have a look at the Word VBA FAQ for a brief intro (the code there is VBA not .Net) and read about it in the VBA help files. Next I would recommend recording a macro while using it. And when you're comfortable with how it works, convert the VBA code (from the macro recorder) to VB.Net.