I know the opposite is easily done with webservices because excel supports webservices for Excel 2013 and up. Maybe it's also possible to send data from Excel via webservice instead of just receiving data from a webservices but to be honest i doubt it.
Most of the ways i can find to ‘send’ data from Excel to somewhere else are basically not Excel sending ianything But are always some export from excel construction to a database or csv, And im guessing that's not what you're looking for in the first place.
I suppose you already tackled the use case, why not use mendix. :)
As already mentioned, excel supports consuming OData services out of the box and not updating OData services out of the box.
If you know some basic VBA, you might be able to create a working prototype based on the code snippets below.
Run macro on cellchange
Run macro on button click
Sending a post request (only works on windows)
One concern however is the security of the webservice.
Either you have to create a public accessible OData API or ask/hardcode the username/password in the vba script.
Another concern is versioning.
Is this Excelsheet stored in Office365/Sharepoint?
In that case you can use Microsoft Flow to set actions on an object that is changed.
Or you can read the last modification date, en possible read, with a direct REST connection to Sharepoint.