Often saving new data in an existing workbook using VBA will cause a pop-up question noting that the file already exists.
To prevent this pop-up question, you have to suppress these types of alerts.
Application.DisplayAlerts = False 'disable user prompt to overwrite file
myWB.SaveAs FileName:="NewOrExistingFilename.xlsx"
Application.DisplayAlerts = True 're-enable user prompt to overwrite file