Excel – Link two excel workbook located in different computers

Across workbooks is not possible, but across worksheets in the same workbook is:
For this private sub, right click the Excel button and hit view code

Private Sub Workbook_TwoWayMatch(ByVal Sh As Object, ByVal Target As Range) 
    If UCase(Sh.Name) = "sheet1" Or UCase(Sh.Name) = "sheet2" Then 
        If Not Application.Intersect(Target, Range("A1")) Is Nothing Then 
            Application.EnableEvents = False 
            If UCase(Target.Parent.Name) = "SHEET1" Then 
                Sheets("Sheet2").Range("A1") = Target 
            Else 
                Sheets("Sheet1").Range("A1") = Target 
            End If 
            Application.EnableEvents = True 
        End If 
    End If 
End Sub 

Nice formatting of your question!

There is no way to turn that on, but there are ways to get it to do it automatically. Enable the developer ribbon if you haven't already (if you have full Excel) and in that ribbon click "Visual Basic"

You want to stick ActiveWorkbook.RefreshAll somewhere. Maybe by editing 'ThisWorkbook' and adding the following code:

Private Sub Workbook_SheetActivate(ByVal Sh As Object)
    ActiveWorkbook.RefreshAll
End Sub

so that it happens every time you switch tabs?

Or maybe by editing the master sheet's VBA code and adding ActiveWorkbook.RefreshAll somewhere in there, like in the Worksheet's Worksheet_Activate or Worksheet_SelectionChange events?

Once you get that working you could also try going to https://stackoverflow.com/questions/211715/how-to-make-a-macro-which-executes-periodically-in-excel to have it periodically update every n seconds instead.