I am trying to calculate the next future invoicing date given an initial renewal date and a increment time (given in months) without using Google scripts or VBA. I have already spent an unreal amount of time trying to do this in Excel with and without VBA but to no avail. Ideally I would like to move this all to Google Sheets but I don’t want to deal with having to deploy custom scripts so anybody could use it. With that said if somebody knows how to do it in either Google Sheets or Excel I would greatly appreciate your input!

In the automation system, I have a google form which is connected with a google sheet called the Main Sheet where the data is getting updated and saved. I have written a code in apps script using toGet() function. The code is executed successfully and data is shown in the output. After that i deploy the script as web app and get the url for it.
In the vba editor, I use the getRESTRICTEDgooglesheets ()function and code is getting executed but the output recieved is not the data in the sheets but an html code for the given scripts tab. What I can do for this??