Actually this would be quite simple but there are more parts so assume this
1. You would use SharePoint or Dataverse or Excel to store the data. I know you said excel, but relatively its all the same and SharePoint would be a better choice than excel for several important reasons but I digress
What I would do
2. Create your Excel File and Add it to SharePoint or Onedrive as it has to be in one of those 2 places (which really just means sharepoint anyway in the back end document library)
3. Create your worksheet and put an Excel Table around the data, as this will be necessary for Power Automate. Now. I will re-tract that and say, it could be done without even in Power Automate but requires calling Graph API. I believe you should not do this for simplification reasons.
4. Add your data and figure out how you are going to add more data, realizing that as you have the file open, the process in Power Automate will NOT work as it will be blocked. This should however not be a problem as you will schedule your flow to run every day at a set time.
5. Make sure you have a column that tracks that you SENT the reminder and what time or at least track what time if you only want 1 instead of 2 columns. I suggest 2 because you want to track when and IF it was successful. is my suggestion
6. Decide if you want people reminded every day for those 30 days or just 1 time as this massively makes a difference in tracking, it doesn't change much in the terms of the below work but I will not where
Now for the work
1. Create a Scheduled Flow for Excel Business Online/Excel
--Configure it to run every day. Pick some time of the day, you know you and no one else will accidentally have it opened and locked.
2. Use List Rows in a Table Excel Action
This allows you to query all the rows in the table
--Add a filter so that it only pulls the rows that meet the criteria based on TODAYS date. So that you only get back the people who need
-----NOTE: If you decide you want to remind them every day for those 30 days (like a countdown) then the filter will have to use a filter like datecolumn is being greater than today and datecolumn being less than DueDate
3. Add an Apply to each (to iterate through each row returned)
inside the action loop
--3a. Assuming the email for the person is in the ROw of data, Add an Send Email V2, to send them an email, using the data from the current Apply to each loop iteration of data
--3b. Use an Update action for excel to update the row that says you send the reminder and when
-----NOTE: This may not work. If the excel file is in use even in the same flow, many times it will say locked and updates will NOT work. TO get around it you have to put a Delay action of up to 10 minutes so it unlocks so you can update it. Now imagine sending 30 emails with a 10 minute delay to update the excel each time.
This is why you should use SharePoint.
Anyway that is it, the work is easy, the flow is easy.
As this answers the question I'd Appreciate if you Marked as such and maybe a like.
If you start to build it and need help specifically, please use the steps and actions I outlined. Then feel free to create another thread to get help, but it is laid out above. Its a big read, but just do the steps in order and it will come together.
