Hi, you can try to check Enable VBA macros option in the Trust Center before running the code.
Click File > Options, in the Excel Options window, select Trust Center from left pane, then go to the Trust Center windown, select Macro Settings, and find this option Enable VBA macros , check it, and click OK > OK.

Hi, MAB, you should make sure that the cell reference in code Range("E1") must be the same with the cell reference that entered the time. Please see the screenshot, the cell A1 contains time, but in the code is B1, then the error pops.

You need to call the Sub procedure "Timer", this is usually done by calling it within another Sub/Function if you want the countdown to begin after you enter a value into cell "A1" and stop when you enter data into another range, then you need to listen for a change to those cells and create a boolean for the Timer sub procedure, so it knows when to stop, to do this create a "Worksheet_Change" sub procedure, this will listen to the worksheet for any changes, we then create a whitelist of ranges that will run our code.


Sub Worksheet_Change(ByVal Target As Range)

'Boolean default value
Dim TimerActive As Boolean: TimerActive = True

'This is where we call the Timer and get our value set in G2
If Not Intersect(Target, Range("A1")) Is Nothing Then

If IsEmpty(Target) Then TimerActive = False: Exit Sub

On Error GoTo Errr:

Dim i As Integer: i = Target

Me.Range("G2").Value = i

Call Timer

ElseIf Not Intersect(Target, Range("B2:C57")) Is Nothing Then

TimerActive = False

If IsEmpty(Target) Then Exit Sub

'Add more code here if needed

End If

'Error processing
Exit Sub
Errr:
MsgBox "A1 Must be integer"

End Sub

I also included the ability to delete the value in A1, which will also stop the countdown, now, in the "Timer" sub procedure, at the beginning create an if statement to check whether or not our boolean "TimerActive" equals False, if it does then we need to Exit Sub. To change the Timers colour when counting down, you need to edit the "ResetTimer" sub procedure, and add an if statement, similar to the one that already exists, "If xRng <= 30", within that statement we add the colour we want to use "xRng.Font.Color = vbRed" you can also change the colour using "xRng.Font.Color = RGB(0,0,0)", do the same in the "Timer" procedure to reset the colour, do this before the boolean if statement, so that the colour always reverts back to its default, even when manually stopped.