You can call it anywhere you like and multiple times. However as you can see from the code you need to include all users in each call:
B4X:
Public Sub SetAutoRefresh(users As List, IntervalMinutes As Double)
AutoRefreshUsers = users
autoRefreshTimer.Interval = IntervalMinutes * DateTime.TicksPerMinute
autoRefreshTimer.Enabled = True
AutoRefresh_Tick
End Sub