I'll have a go anyway. Download Recuva from http/www.piriform.com and Restoration 2514 from http/www.win-freeware.com/REST2514.htm. Try using both recover files of type .xls (or xlsx if Office 2007/10) and see what you get back. If they haven't been specifically overwritten, you may bne lucky.
You are unlikely to recover an over written Excel file. Basically files are saved in "data chucks" on a hard drive which is divided up into sectors. When a file is saved over, the "data chunks" are overwritten in the same sectors the original file occupied (more or less). The larger the file the more sectors are used, the smaller the file the fewer sectors are used.
To speak plainly, when a sector is overwritten with new data, the old data is gone.
@kschok If you are searching and started thread to recover that file back, that must be important. Onboard is actually very right, once file is overwritten it can not be recovered easily. For that you can contact data recovery service
provider. As he said for that Class 100 Clean rooms are required.