VB To Edit Another Workbook

My purpose is to give my endusers a workbook with a macro in it which applies changes to existing workbooks on their computers. I want the enduser to select each workbook to apply the changes and have the macro capture the names of the workbooks so they can verify that all of the appropriate workbooks have been changed.

I’m trying to change two types of data: (1) text, (2) formulas.

Here's what little I have, but not much is working.

Sub ChangeBACKLOG()
MsgBox "Open the FILE to which the Backlog fix is to be applied."
Dim targetWorkbook
dlgSource = Application.Dialogs(xlDialogOpen).Show

Set sourceWorkbook = ThisWorkbook
Set targetWorkbook = Workbooks.Item(Workbooks.Count)

On Error Resume Next