Start and Stop on Application.Ontime...

Option Explicit

Public RunWhen As Double
Public Const cStartTime = "09:30:00"
Public Const cEndTime = "16:00:00"
Public Const cRunInterval = "00:15:00"
Public Const cRunWhat = "Index_Analysis"  'name of procedure to run


Public Sub StartTimer()
    'If current time is earlier than start time, schedule the macro to start today, otherwise the start time has already passed so start
    'it tomorrow
    
    If Now < Int(Now) + TimeValue(cStartTime) Then
        RunWhen = Int(Now) + TimeValue(cStartTime)
    Else
        RunWhen = Int(Now) + 1 + TimeValue(cStartTime)
    End If
    Application.OnTime EarliestTime:=RunWhen, Procedure:=cRunWhat, Schedule:=True
End Sub

Public Sub RestartTimer()
    Dim d As Integer
    
    'If end time is earlier than start time then time range spans midnight so add 1 day to end time to make it occur tomorrow
    
    d = 0
    If TimeValue(cEndTime) < TimeValue(cStartTime) Then d = 1

    'If current time is earlier than end time, reschedule the macro to run again after the time interval, otherwise stop the timer

    If Now < Int(Now) + d + TimeValue(cEndTime) Then
        RunWhen = Now + TimeValue(cRunInterval)
        Application.OnTime EarliestTime:=RunWhen, Procedure:=cRunWhat, Schedule:=True
    Else
        StopTimer
    End If
End Sub

Public Sub StopTimer()
    On Error Resume Next
    Application.OnTime EarliestTime:=RunWhen, Procedure:=cRunWhat, Schedule:=False
    MsgBox cRunWhat & " stopped"
End Sub


Sub Index_Analysis()
        
    'Call StartTimer to schedule the procedure again
    RestartTimer
    
    'Put your code here
    '==================
      
End Sub

Private Sub Workbook_Open()
    StartTimer
End Sub

Private Sub Workbook_BeforeClose(Cancel As Boolean)
    StopTimer
End Sub