Final goal: to get a notification with a list of changes in installed programs. I don't need a list of all programs, just a list of changes. 

I have created an item called winsoft, it contains a list of installed programs with the help of a command in json (system.run[powershell -c "Get-Package | ConvertTo-Json"]). Next I want to create another item that will compare the last two recent values in winsoft and store the difference. Then I will create a trigger on the changes vinsoft difference.

Question, is it possible to create an aitem that will store the difference of the last two values? Right now I see only one way to do it through api.