Private Sub Workbook_Open()
Dim x As Date, m As Integer, y As Integer
x = Int(Now())
m = Month(x)
y = Year(x)
If m = 12 Then
LastDayOfThisMonth = DateValue(m & "/" & 31 & "/" & y)
Else
LastDayOfThisMonth = DateAdd("d", -1, DateValue(m + 1 & "/" & 1 & "/" & y))
End If
LastDay = Weekday(LastDayOfThisMonth)
Select Case LastDay
Case 1
LastWeekDay = Month(LastDayOfThisMonth) & "/" & Day(LastDayOfThisMonth) - 2 & "/" & Year(LastDayOfThisMonth)
Case 2 To 6
LastWeekDay = Month(LastDayOfThisMonth) & "/" & Day(LastDayOfThisMonth) & "/" & Year(LastDayOfThisMonth)
Case 7
LastWeekDay = Month(LastDayOfThisMonth) & "/" & Day(LastDayOfThisMonth) - 1 & "/" & Year(LastDayOfThisMonth)
End Select
If LastWeekDay = Date Then
MsgBox "Today is the last week day of this month."
'''Your code for the last week day of this month goes here
Else
MsgBox "The last week day of this month is " & LastWeekDay
'''Your code (if any) for every other day of the month goes here
End If
End Sub