Timer Question

Guys and gals

I am working on a sketch that monitors a bunch of sensors.

One requirement is that on execution of an I/P, I need to run a timer for 5,10 or 15 mins., that doesn't affect the operation of the main loop, and generates an interrupt or sets a flag on completion.

Can this be done using the internal timer registers, or would I need to include a RTC?

TIA Fof

Blink-without-delay is the correct choice.

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The sooner you do, the happier you will be.

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Brilliant, guys.

Thank you.