Define updating/modifying time as a timepoint

Hi friends,
I have connected an excell file as my database on the sharepoint to the Power Bi and then refresh it as I add new subjects with different IDs to the spreadsheet weekly. Now, I need to compare the number of subjects with the previous report and have a trend (increase or decrease) in that number based on each update (consider the updates as timepoints as I do not have any other date as reference), if anyone can advise please. Hope it is clear. Thanks in advance.