Это должно делать то, что вы хотите.
Sub OpenAllExcelFiles()
Dim wb As Workbook, wbCSV As Workbook
Dim sPath As String, sFilename As String
Dim NbRows As Integer, rg As Range
Set wb = ThisWorkbook
Application.ScreenUpdating = False
sPath = "C:\your_path\" 'Path of CSV Files
sFilename = Dir(sPath & "*.xlsx")
Do While Len(sFilename) > 0
Set wbCSV = Workbooks.Open(sPath & sFilename) 'open file
NbRows = wbCSV.Sheets(1).Range("A100").End(xlUp).Row 'nb of rows
Set rg = wb.Sheets(1).Range("A100").End(xlUp).Offset(1, 0)
rg = sFilename
rg.Offset(0, 1) = NbRows
wbCSV.Close False 'close file
sFilename = Dir
Loop
Application.ScreenUpdating = True
End Sub
Окончательный результат в моем тестовом примере:
![enter image description here](https://i.stack.imgur.com/K95Pw.png)