code verbessern

Private Sub UserForm_Activate()
Dim a As String
a = Date
If a = #3/1/2004# Then
a = Sheets("post").Range("cn10")
ElseIf a = #3/2/2004# Then
a = Sheets("post").Range("cn11")
ElseIf a = #3/3/2004# Then
a = Sheets("post").Range("cn12")
ElseIf a = #3/4/2004# Then
a = Sheets("post").Range("cn13")
ElseIf a = #3/5/2004# Then
a = Sheets("post").Range("cn14")
ElseIf a = #3/6/2004# Then
a = Sheets("post").Range("cn15")
ElseIf a = #3/7/2004# Then
a = Sheets("post").Range("cn16")
ElseIf a = #3/8/2004# Then
a = Sheets("post").Range("cn17")
ElseIf a = #3/9/2004# Then
a = Sheets("post").Range("cn18")
ElseIf a = #3/10/2004# Then
a = Sheets("post").Range("cn19")
ElseIf a = #3/11/2004# Then
a = Sheets("post").Range("cn20")
ElseIf a = #3/12/2004# Then
a = Sheets("post").Range("cn21")
ElseIf a = #3/13/2004# Then
a = Sheets("post").Range("cn22")
ElseIf a = #3/14/2004# Then
a = Sheets("post").Range("cn23")
ElseIf a = #3/15/2004# Then
a = Sheets("post").Range("cn24")
ElseIf a = #3/16/2004# Then
a = Sheets("post").Range("cn25")
ElseIf a = #3/17/2004# Then
a = Sheets("post").Range("cn26")
ElseIf a = #3/18/2004# Then
a = Sheets("post").Range("cn27")
ElseIf a = #3/19/2004# Then
a = Sheets("post").Range("cn28")
ElseIf a = #3/20/2004# Then
a = Sheets("post").Range("cn29")
ElseIf a = #3/21/2004# Then
a = Sheets("post").Range("cn30")
ElseIf a = #3/22/2004# Then
a = Sheets("post").Range("cn31")
ElseIf a = #3/23/2004# Then
a = Sheets("post").Range("cn32")
ElseIf a = #3/24/2004# Then
a = Sheets("post").Range("cn33")
ElseIf a = #3/25/2004# Then
a = Sheets("post").Range("cn34")
ElseIf a = #3/26/2004# Then
a = Sheets("post").Range("cn35")
ElseIf a = #3/27/2004# Then
a = Sheets("post").Range("cn36")
ElseIf a = #3/28/2004# Then
a = Sheets("post").Range("cn37")
ElseIf a = #3/29/2004# Then
a = Sheets("post").Range("cn38")
ElseIf a = #3/30/2004# Then
a = Sheets("post").Range("cn39")
ElseIf a = #3/31/2004# Then
a = Sheets("post").Range("cn40")
Else
a = Sheets("post").Range("cn40")
End If
txtMonat.Value = Date
TextBox2.Value = a
End Sub