Сначала преобразуем строку в дату. Затем добавьте логику.
Dim strDate As String
Dim dteDate As Date
strDate = "11012019" 'This is the string date
strMonth = Left(strDate, 2) 'Get the month
strDay = Mid(strDate, 3, 2) 'Get the day
strYear = Right(strDate, 4) 'get the year
dteDate = DateSerial(strYear, strMonth, strDay) 'string converted to date
If Date < dteDate Then
MsgBox "Date is a future date."
Else
MsgBox "Date is either today or in the past."
End If