Quick Coding Question about Custun Indicators

 
Does anyone know if an indicator can have a timer applied ?

I have an email alert that I want to use for the London session but I only want it to activate at times around the session open (plus and minus ~1hr from the session open, say 1am to 3:30am). I dont want to wake up unless the trade opportunity is optimum. I would like to apply the indicator to my chart but have it 'wake up' at a specific times. Thank you
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