Thank you, Mike. In fact, what I did was created some form fields in a word document, these form fields are also the bookmarks. Then I built a VFP form to capture users' input and I try to pass the data to those form fields.
Anyway, I've worked out the solution:
oWord = CreateObject("Word.Application"

oWord.DisplayAlerts = .F.
** open the word document containing the form fields.
oWordDoc = oWord.Documents.Open("C:\temp\test\test.doc"

** to get the form field's name: right click on a form
** field in your word document --> Field Setting
** --> Bookmark
oWordDoc.FormFields("form_field_name"

.Result = thisform.text1.value
oWordDoc.PrintOut()
oWord.Quit()
RELEASE oWord