Countdown problem

I have some coding that does a countdown, however, it does the first second then doesn't show the countdown from then on. It only counts down when I close down and open again....not that helpful!!!

Is there a way to keep the countdown running? (I know it is running in the background).

Here is some of the code I am using.

Code below:

Sub sheet_calc()
dt = 1 / 24 / 60 / 60
t = Range("d27").Value
If t > -dt Then
Application.OnTime Now + TimeValue("00:00:01"), "sheet_calc"
If t < dt Then Application.Speech.Speak "Warning. warning. warning. warning. warning"


ActiveSheet.Calculate
End If
End Sub

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Private Sub CommandButton1_Click()
Range("N2").Value = Now
End Sub

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In cell Q1 I have this formula

=N1+P1-NOW()

Cell N1 has the date and time in this format: dd/mm/yyyy h:mm
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And I have 2 macros that has this:

Macro 1:

Range("P1").Select


ActiveCell.FormulaR1C1 = "12:01:00 AM"
Range("P2").Select

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Macro 2:

Application.Run "timer.xltm!sheet_calc"

Very messy I know, is there a better way?

Thanks.