One Sheet Manual Calculation

Hi SHG, I was thinking to do something like you proposed. but I do not know how to call the secod sub when any change happen in the workbook.
any hint in that sense will be great

'First part when the workbook is opened
Private Sub Workbook_Open()
    'To disable Excel Automatic Calculation then all sheet are frozen
    With Application
        .Calculation = xlManual
        .CalculateBeforeSave = False
    End With
    'making sure that check box is false
    Sheet1.CheckBox1.Value = False
    Sheet1.Range("M2") = "FALSE"
    
    'to calculate only the sheets with the true condition when the workbook is open
    'sheet3 and 4 to update results
    Sheet3.Calculate
    Sheet4.calcualate
    'sheet 1 to update results
    Sheet1.Calculate
End Sub


'second part
'This is the bit that I do not know how to do it
'When any change happen in the workbook any of the sheets even shhet 2
    'calculate only the sheets with the true condition stated in sheet1(eg. sheet3 and 4 first to update results)
    'Sheet3.Calculate
    'Sheet4.calcualate
    
    'check if sheet2 has to be calculated (if the user tick the check box
    'If Sheet1.Range("M2") = "TRUE" Then
    '    Sheet2.Calculate
    'Else
    'End If
    
    'sheet 1 to update all results from sheet2,3,4
    'Sheet1.Calculate

'End