How to run VBA macro in win32 when used as a variable

I am writing a script which opens an excel sheet and enters some data and runs a VBA macro.

import os
import win32com.client
import glob

xl=win32com.client.Dispatch("Excel.Application")
working_dir = os.getcwd()

path = os.path.join(working_dir, 'folder')
file_list = glob.glob(path + '/*.xls*')
for file in file_list:
    file_name = str(file)
    wb = xl.Workbooks.Open(file_name)
    wb.Worksheets("sheet1").Activate()
    ws = wb.Activesheet.Name
    ws1 = wb.Worksheets(ws)
    ws1.Range("E5").FormulaR1C1 = "add_text_here"
    xl.Goto(ws1.Range('E5'))
    xl.Run("excel_sheet.xls!macro")
    wb.Close(SaveChanges=True)
    xl.Quit()

I am able to run this script properly. The problem I get is, when I change the run macro to read from a variable like below.

xl.Run(file_name+"!macro") # here I changed file name to a variable

I get

The macro may not be available in this workbook or all macros may be disabled.", 'xlmain11.chm', 0, -2146827284), None)

error.

I really need to do this because I dont want to give the Excel file name hard coded and this Excel file may change. Please help me.