In that case, the server asynchronously generates a response upon the JS request. It then gives you a data stream back that is of the Content-Type application/vnd.ms-excel; additionally, it is marked with Content-Disposition: attachment; filename=Cuentas por entidad.xls.
What all this indicates is that you will only get that datastream neatly packed into a file for download as a response to said JS event. It is not cached on the server in any way, it's really just "handmade" for you on the fly.
Thus, there is no http location of that file. It only exists temporarily on your end as a browser-cached response.
You could maybe set up an appropriate POST that reliably results in that response, when I look at the output of Live HTTP headers after clicking the link though, it doesn't look like it. The server appears to evaluate multiple runtime arguments and then gives the appropriate response; maybe you can guess them, but I don't think so.