Tag the controls in the userform to match the names of the bookmarks in the source documents:

Private Sub CommandButton1_Click()
Dim varBMArray() As Variant, lngIndex As Integer
Dim oDlg As FileDialog, Bcnt As Integer, WdStart As Boolean
Dim oDocSource As Document
Dim oCtrl
  Set oDlg = Application.FileDialog(msoFileDialogFilePicker)
  With oDlg
    .Title = ("Select File and Click OK")
    .AllowMultiSelect = False
    .Filters.Add "Word Files", "*.doc; *.docx; *.docm; *.dotx;*.dot", 1
    If .Show = 0 Then
       MsgBox ("No file was selected.")
       Exit Sub
    End If
  End With
  Set oDocSource = Documents.Open(oDlg.SelectedItems(1), , , , , , , , , , , False)
  If oDocSource.Bookmarks.Count > 0 Then
    ReDim varBMArray(oDocSource.Bookmarks.Count - 1, 1)
    For lngIndex = 0 To oDocSource.Bookmarks.Count - 1
      varBMArray(lngIndex, 0) = oDocSource.Bookmarks(lngIndex + 1).Name
      varBMArray(lngIndex, 1) = oDocSource.Bookmarks(lngIndex + 1).Range.Text
    Next lngIndex
  Else
    MsgBox "No bookmarks"
  End If
  oDocSource.Close wdDoNotSaveChanges
  For lngIndex = 0 To UBound(varBMArray)
    For Each oCtrl In Me.Controls
      If oCtrl.Tag = varBMArray(lngIndex, 0) Then
        oCtrl.Value = varBMArray(lngIndex, 1)
        Exit For
      End If
    Next oCtrl
  Next lngIndex
  
lbl_Exit:
  Exit Sub
End Sub