with pd.ExcelWriter('C:\\Projects\\BOXES\\BOXED.xlsx') as writer:
    for B in BOX:
        filename = B + '.xls'
BDF = pd.read_excel('C:\\Projects\\BOXES\\\\' + filename)
BDF = BDF.dropna(how='all')
BDF['Total Cost'] = BDF['Total Cost'].str.replace('.', '')
BDF.columns = ['LVL', 'PN', 'Leadtime', 'Description', 'Ext QTY']
BDF.PN = BDF.PN.str.strip()
sheetname = B
BDF.to_excel(writer, sheet_name=B, index=False)
del BDF
cleaning multiple documents and saving them to one book with a loop in Pandas