Attribute VB_Name = "LoopFilesInFolder"
' Loops through every .xlsx in a chosen folder and prints the file name + row count.
Sub LoopFilesInFolder()
    Dim folderPath As String, file As String
    Dim wb As Workbook, n As Long
    With Application.FileDialog(msoFileDialogFolderPicker)
        If .Show <> -1 Then Exit Sub
        folderPath = .SelectedItems(1) & "\"
    End With

    file = Dir(folderPath & "*.xlsx")
    Do While file <> ""
        Set wb = Workbooks.Open(folderPath & file, ReadOnly:=True)
        Debug.Print file, wb.Sheets(1).UsedRange.Rows.Count
        wb.Close SaveChanges:=False
        n = n + 1
        file = Dir
    Loop
    MsgBox "Processed " & n & " files. See the Immediate window (Ctrl+G).", vbInformation
End Sub