Option Explicit
Public Sub Beispiel()
Dim dic As Object
Dim dtm(0 To 4) As Date
Dim key0 As String
Dim keyJ As String
Dim i As Long
Dim j As Long
For i = 3 To 5
dtm(0) = Worksheets("data").Cells(i, "C").Value
dtm(1) = Worksheets("data").Cells(i, "D").Value
dtm(2) = Worksheets("data").Cells(i, "E").Value
dtm(3) = Worksheets("data").Cells(i, "F").Value
dtm(4) = Worksheets("data").Cells(i, "G").Value
key0 = Format$(dtm(0), "yyyy-mm-01")
Set dic = CreateObject("Scripting.Dictionary")
For j = 1 To 4
keyJ = Format$(dtm(j), "yyyy-mm-01")
If CDate(key0) < CDate(keyJ) Then
If Not dic.Exists(keyJ) Then
dic(keyJ) = Empty
End If
End If
Next
Worksheets("data").Cells(i, "B").Value = dic.Count
Next
End Sub