Vba - Check String/Text From Multiple Workbook Without Opening All Files

[p45cal]

Late in the day, I know. This one looks for strings only (numbers are ignored) in that range:

Sub blah()
Set fs = CreateObject("Scripting.FileSystemObject")
Pth = "D:\Target"
Set f = fs.GetFolder(Pth)
For Each wb In f.Files
  If InStr(1, wb.Type, "Excel", vbTextCompare) > 0 Then
    With Range("C4") 'use a cell where it doesn't matter
      .Formula2R1C1 = "=SUMPRODUCT(--ISTEXT('" & Pth & "\[" & wb.Name & "]Sheet1'!R6C1:R11C15))"
      If .Value > 0 Then If Len(msg) = 0 Then msg = wb.Name Else msg = msg & vbLf & wb.Name
      .Clear
    End With
  End If
Next wb
If Len(msg) > 0 Then
  MsgBox "Workbooks containing any string in range B6:O11 are:" & vbLf & msg
Else
  MsgBox "None found"
End If
End Sub

https://www.youtube.com/channel/UCnxwq2aGJRbjOo_MO54oaHA