Help need: Design of requesting more usage time on demand.

[lifei]

I'm writing a feature of requesting more usage time for special app on demand.

A kid can submit a request for more usage time of a app.

after approved, an activity event is monitored.

but if the kid submit another request:

1. for the same app: the usage time should be plused together, but no api can do this, you can not get the current total usage time first.
2. for another app: the activity event can not be merge with two app. the event name must be defined at the very beginning, can not be defined by apps.

so how to solve these issues. thanks.