[vba] Open a workbook using FileDialog and manipulate it in Excel VBA

I am learning how to use Excel macros and I found this code:

Dim fd As Office.FileDialog

Set fd = Application.FileDialog(msoFileDialogFilePicker)

With fd

    .AllowMultiSelect = False
    .Title = "Please select the file to kill his non colored cells"
    .Filters.Add "Excel", "*.xls"
    .Filters.Add "All", "*.*"

    If .Show = True Then
        txtFileName = .SelectedItems(1)
    End If

End With

This code opens the FileDialog. How can I open the selected Excel file without over-writing the previously opened?

Unless I misunderstand your question, you can just open a file read only. Here is a simply example, without any checks.

To get the file path from the user use this function:

Private Function get_user_specified_filepath() As String
    'or use the other code example here.
    Dim fd As Office.FileDialog
    Set fd = Application.FileDialog(msoFileDialogFilePicker)
    fd.AllowMultiSelect = False
    fd.Title = "Please select the file."
    get_user_specified_filepath = fd.SelectedItems(1)
End Function

Then just open the file read only and assign it to a variable:

dim wb as workbook
set wb = Workbooks.Open(get_user_specified_filepath(), ReadOnly:=True)