I would do something like this:
Context: Notification, Owner App: Calendar
Context: Variable Value, %SILENT = on/vibrate
Task:
Variable Set %CALNOT = 1
Context: Variable Value %CALNOT Is Set
Enter Task:
Silent Mode Off
Notification Volume 7
Notify Sound, Title: CalNot
Notify Cancel, Title: CalNot
Variable Clear %CALNOT
By using two profiles, you're using the event context (Notification)
to initiate a state context.(Variable Value). The advantage is that
the settings you change (silent mode, notification volume) will return
to their previous states once the profile exits, which will be as soon
as the enter task completes (because the task clears the variable).