'in un modulo
Option Explicit

Public RunWhen As Double
Public cRunIntervalSeconds As Integer    'secondi
Public Const cRunWhat = "TheSub"

Sub StartTimer()
    cRunIntervalSeconds = [A2]
    If cRunIntervalSeconds = 0 Then MsgBox "Inserire in A2 un numero diverso da zero.": Exit Sub
    If Val([C4]) = 0 Then [C2] = "Running."
    RunWhen = Now + TimeSerial(0, 0, cRunIntervalSeconds)
    Application.OnTime EarliestTime:=RunWhen, Procedure:=cRunWhat, Schedule:=True
End Sub

Sub TheSub()
    [C4] = [C4] + 1
    StartTimer  ' Reschedule the procedure
End Sub

Sub StopTimer()
    On Error Resume Next
    Application.OnTime EarliestTime:=RunWhen, Procedure:=cRunWhat, Schedule:=False
    [C4].CurrentRegion.ClearContents
    [C2] = "Stopped."
End Sub

Option Explicit
    Public TimeOld As Variant
'---Funzione per calcolare il tempo del ciclo
Declare Function GetTickCount Lib "kernel32" () As Long

Public Declare Function SetTimer Lib "user32" ( _
    ByVal HWnd As Long, _
    ByVal nIDEvent As Long, _
    ByVal uElapse As Long, _
    ByVal lpTimerFunc As Long) As Long

Public Declare Function KillTimer Lib "user32" ( _
    ByVal HWnd As Long, _
    ByVal nIDEvent As Long) As Long

    Public TimerID_1 As Long
    Public TimerID_2 As Long
    
    Public TimerSeconds As Single
    
 
 Sub StartTimer_1()
    Dim speed As Variant
    speed = Foglio1.[A4] / 1000
    Foglio1.[C4] = "Running."
    If speed = 0 Then speed = 1
    TimerSeconds = 0.1  ' how often to "pop" the timer.
    TimerID_1 = SetTimer(0&, 0&, (TimerSeconds * 2500) + ((((TimerSeconds * 2500) / 10) * speed) / 10), AddressOf TimerProc_1) '0,5 secondi
 End Sub

 Sub EndTimer_1()
    On Error Resume Next
    KillTimer 0&, TimerID_1
    Foglio1.[C4] = "Stopped."
 End Sub

 Sub TimerProc_1(ByVal HWnd As Long, ByVal uMsg As Long, _
    ByVal nIDEvent As Long, ByVal dwTimer As Long)
    On Error Resume Next
    Foglio1.[C6] = Foglio1.[C6] + Foglio1.[A4] / 1000
    DoEvents
 End Sub
 '------------------------------------------------------------
 Sub StartTimer_2()
    Dim speed As Variant
    speed = Foglio1.[E4] / 1000
    Foglio1.[G4] = "Running."
    If speed = 0 Then speed = 1
    TimerSeconds = 0.1  ' how often to "pop" the timer.
    TimerID_2 = SetTimer(0&, 0&, (TimerSeconds * 2500) + ((((TimerSeconds * 2500) / 10) * speed) / 10), AddressOf TimerProc_2) '0,5 secondi
 End Sub

 Sub EndTimer_2()
    On Error Resume Next
    KillTimer 0&, TimerID_2
    Foglio1.[G4] = "Stopped."
 End Sub

 Sub TimerProc_2(ByVal HWnd As Long, ByVal uMsg As Long, _
    ByVal nIDEvent As Long, ByVal dwTimer As Long)
    On Error Resume Next
    Foglio1.[G6] = Foglio1.[G6] + Foglio1.[E4] / 1000
    DoEvents
 End Sub