For Each ndr As DataRow In dt_tj.Select("")
改成
Dim d As Date = date.Today
Dim pd As Date = d.AddMonths(-1)
For Each ndr As DataRow In dt_tj.Select("年份 = '" & pd.Year & "' and 月份 = '" & pd.Month & "' or 年份 = '" & d.Month & "' and 月份 = '" & d.Month & "'")