You have to open, or create, the documents to process and process them separately e.g.
Private Sub CommandButton1_Click()
Dim oRng As Range
Dim oDoc1 As Document
Dim oDoc2 As Document
Dim oDoc3 As Document
'create (or open) the documents
Set oDoc1 = Documents.Add("C:\Path\Template1.dotx")
Set oDoc2 = Documents.Add("C:\Path\Template2.dotx")
Set oDoc3 = Documents.Add("C:\Path\Template3.dotx")
'process each document
'fname
If oDoc1.Bookmarks.Exists("fname") = True Then
Set oRng = oDoc1.Bookmarks("fname").Range
oRng.Text = TextBox1.value
oDoc1.Bookmarks.Add "fname", oRng
End If
If oDoc2.Bookmarks.Exists("fname") = True Then
Set oRng = oDoc2.Bookmarks("fname").Range
oRng.Text = TextBox1.value
oDoc2.Bookmarks.Add "fname", oRng
End If
If oDoc3.Bookmarks.Exists("fname") = True Then
Set oRng = oDoc3.Bookmarks("fname").Range
oRng.Text = TextBox1.value
oDoc3.Bookmarks.Add "fname", oRng
End If
'lname
If oDoc1.Bookmarks.Exists("lname") = True Then
Set oRng = oDoc1.Bookmarks("lname").Range
oRng.Text = TextBox2.value
oDoc1.Bookmarks.Add "lname", oRng
End If
If oDoc2.Bookmarks.Exists("lname") = True Then
Set oRng = oDoc2.Bookmarks("lname").Range
oRng.Text = TextBox2.value
oDoc2.Bookmarks.Add "lname", oRng
End If
If oDoc3.Bookmarks.Exists("lname") = True Then
Set oRng = oDoc3.Bookmarks("lname").Range
oRng.Text = TextBox2.value
oDoc3.Bookmarks.Add "lname", oRng
End If
'address
If oDoc1.Bookmarks.Exists("address") = True Then
Set oRng = oDoc1.Bookmarks("address").Range
oRng.Text = TextBox3.value
oDoc1.Bookmarks.Add "address", oRng
End If
If oDoc2.Bookmarks.Exists("address") = True Then
Set oRng = oDoc2.Bookmarks("address").Range
oRng.Text = TextBox3.value
oDoc2.Bookmarks.Add "address", oRng
End If
If oDoc3.Bookmarks.Exists("address") = True Then
Set oRng = oDoc3.Bookmarks("address").Range
oRng.Text = TextBox3.value
oDoc3.Bookmarks.Add "address", oRng
End If
'dob
If oDoc1.Bookmarks.Exists("dob") = True Then
Set oRng = oDoc1.Bookmarks("dob").Range
oRng.Text = TextBox4.value
oDoc1.Bookmarks.Add "dob", oRng
End If
If oDoc2.Bookmarks.Exists("dob") = True Then
Set oRng = oDoc2.Bookmarks("dob").Range
oRng.Text = TextBox4.value
oDoc2.Bookmarks.Add "dob", oRng
End If
If oDoc3.Bookmarks.Exists("dob") = True Then
Set oRng = oDoc3.Bookmarks("dob").Range
oRng.Text = TextBox4.value
oDoc3.Bookmarks.Add "dob", oRng
End If
'amount
If oDoc1.Bookmarks.Exists("amount") = True Then
Set oRng = oDoc1.Bookmarks("amount").Range
oRng.Text = TextBox5.value
oDoc1.Bookmarks.Add "amount", oRng
End If
If oDoc2.Bookmarks.Exists("amount") = True Then
Set oRng = oDoc2.Bookmarks("amount").Range
oRng.Text = TextBox5.value
oDoc2.Bookmarks.Add "amount", oRng
End If
If oDoc3.Bookmarks.Exists("amount") = True Then
Set oRng = oDoc3.Bookmarks("amount").Range
oRng.Text = TextBox5.value
oDoc3.Bookmarks.Add "amount", oRng
End If
'period
If oDoc1.Bookmarks.Exists("period") = True Then
Set oRng = oDoc1.Bookmarks("period").Range
oRng.Text = TextBox6.value
oDoc1.Bookmarks.Add "period", oRng
End If
If oDoc2.Bookmarks.Exists("period") = True Then
Set oRng = oDoc2.Bookmarks("period").Range
oRng.Text = TextBox6.value
oDoc2.Bookmarks.Add "period", oRng
End If
If oDoc3.Bookmarks.Exists("period") = True Then
Set oRng = oDoc3.Bookmarks("period").Range
oRng.Text = TextBox6.value
oDoc3.Bookmarks.Add "period", oRng
End If
Unload Me
End Sub