auto save two excel copied with two different format

I have an excel with (.xmlx) formate that contains some features,
I need to save the excel as (.xls) format, but I have an issue, the data validation is removed from the new format.

So, I need to :
once I save the file with (.xmlx), automatically other copy of file with (.xls) format will be created.

or if there is any other solution to have two identical files (one with (.xls) format and the other with (.xmlx) format)?

Thanks.