Option Explicit
Sub ImportCSVsWithReference()

Dim wbCSV   As Workbook
Dim wsMstr  As Worksheet:   Set wsMstr = ThisWorkbook.Worksheets("Sheet")
Dim fPath   As String:      fPath = "C:\work\"    'path to CSV files, include the final \
Dim fCSV    As String

If MsgBox("Clear the existing MasterCSV sheet before importing?", vbYesNo, "Clear?") _
    = vbYes Then wsMstr.UsedRange.Clear

Application.ScreenUpdating = False  

fCSV = Dir(fPath & "*.csv")        

    Do While Len(fCSV) > 0
      'open a CSV file
        Set wbCSV = Workbooks.Open(fPath & fCSV)
      'insert col A and add CSV name
        Columns(1).Insert xlShiftToRight
        Columns(1).SpecialCells(xlBlanks).Value = ActiveSheet.Name
      'copy date into master sheet and close source file
        ActiveSheet.UsedRange.Copy wsMstr.Range("A" & Rows.Count).End(xlUp).Offset(1)
        wbCSV.Close False
      'ready next CSV
        fCSV = Dir
    Loop
 
Application.ScreenUpdating = True
End Sub
Sub delete()
Columns(7).delete
End Sub

Sub AAA()
Call ImportCSVsWithReference
Call delete
End Sub