Let's say we have a group of workbooks in a folder and we suspect that on
some sheet of some workbook the function =SUM() is being used.  We want to
find the workbook, the sheet, and the cell holding the function:

1. open the workbooks in the folder
2. run the following:

Sub findit()
For Each wb In Workbooks
   wb.Activate
   For Each sh In wb.Sheets
       sh.Activate
       For Each r In sh.UsedRange
           v = r.Formula
           If InStr(v, "SUM(") > 0 Then
               r.Select
               Exit Sub
           End If
       Next
   Next
Next
End Sub

Clearly this code can be modified to open each workbook in series.