A family of Microsoft word processing software products for creating web, email, and print documents.
Using VBA,
Dim rngPage as Range
Set rngPage = ActiveDocument.Bookmarks("\page").Range
will set a rngPage to the Range of the page on which the Selection is located.
Then you could use
With rngPage
.Text = Replace(.Text, "old text to be replaced", "new text to be used")
End With