B列がシリアル値でなくyyyy/mmの7文字の文字列の場合です。翌月以降とのことなので、単純に65歳になる年だけ月のみを比較してます。
Sub Sample()
Dim i As Long, n As Long
Dim key1 As Date, tmp
Dim key0 As Range, buf As Range
Set key0 = Range(\u0026quot;A2\u0026quot;)
For i = 2 To 13
Set buf = Cells(i, \u0026quot;B\u0026quot;)
tmp = Split(buf.Value, \u0026quot;/\u0026quot;)
key1 = DateSerial(tmp(0), tmp(1), 1)
Select Case Year(key1) - Year(key0.Value)
Case Is \u0026gt; 65: n = n + Cells(i, \u0026quot;C\u0026quot;).Value
Case 65: If Month(key1) \u0026gt; Month(key0) Then n = n + Cells(i, \u0026quot;C\u0026quot;).Value
End Select
Next i
Range(\u0026quot;D14\u0026quot;).Value = \u0026quot;合計 \u0026quot; \u0026amp; n \u0026amp; \u0026quot; 円\u0026quot;
End Sub