Thanks for posting! Unfortunately, it is not currently possible to push changes from Lucidchart to a data source. Additionally, because Excel data files are locally stored rather than accessible online, Lucidchart does not have access to changes you make to the excel sheet unless to re-import the source.
If you would like to be able to refresh data from your source, I recommend transferring your data from Excel to a Google Sheet. If you would like to see bi-lateral sync between Lucidchart and Google Sheets, can you please add this request to our feature request form?