Convert multiple txt files in folder to csv

Try this:

Dim oFSO, myFolder
Dim xlCSV

myFolder="C:\your\path\to\excelfiles\"


Set oFSO = CreateObject("Scripting.FileSystemObject")
xlCSV = 6 'Excel CSV format enum
Call ConvertAllExcelFiles(myFolder)
Set oFSO = Nothing

Call MsgBox ("Done!")


Sub ConvertAllExcelFiles(ByVal oFolder)
Dim targetF, oFileList, oFile
Dim oExcel, oWB, oWSH

    Set oExcel = CreateObject("Excel.Application")
    oExcel.DisplayAlerts = False
    Set targetF = oFSO.GetFolder(oFolder)
    Set oFileList = targetF.Files
    For Each oFile in oFileList
        If (Right(oFile.Name, 4) = "xlsx") Then
            Set oWB = oExcel.Workbooks.Open(oFile.Path)
            For Each oWSH in oWB.Sheets
                Call oWSH.SaveAs (oFile.Path & oWSH.Name & ".csv", xlCSV)
            Next
            Set oWSH = Nothing
            Call oWB.Close
            Set oWB = Nothing
        End If
    Next
    Call oExcel.Quit
    Set oExcel = Nothing

End Sub