Excel comparator

Private Sub CheckDate_Click()

Dim i As Integer, r As Integer, num As Integer
Dim T1, T2 As Date
Dim lie As Integer

lie = 15 ' Column number 15  namely  O  Column 
num = 0 ' Count the due quantity of the next calibration date 

r = Range("o65536").End(xlUp).Row ' Statistics o How many cells have data in the column 

T2 = Now() - 30 ' The current date is forward 30 God 

'T1 = VBA.DateSerial(2022, 6, 26)' Date conversion 
'T1 = Range("A1").Value' Get cell value 

' Cycle cell data 
For i = 1 To r
T1 = Cells(i, lie)

If (IsEmpty(T1)) Then
    Cells(i, lie).Interior.Pattern = xlNone ' Clear background color 
ElseIf (T1 < T2) Then
    'MsgBox (" The calibration date of the instrument has expired ")
    Cells(i, lie).Interior.Color = 255 ' Fill in red 
    num = num + 1
Else
    Cells(i, lie).Interior.Pattern = xlNone ' Clear background color 
End If

Next

If (num > 0) Then
    Dim result
    result = MsgBox(" All in all " + Str(num) + " Devices expire , Need to arrange correction ！", vbExclamation)
End If


End Sub