When IFs get complicated, using Select Case may make things easier
For 'short' ranges; can handle 'exceptions' too:
Select Case DateDiff("d", dtA, dtB) ' computed just once automagically
Case 1, 2, 3, 5 ' effectively OR without the noise => risk of messing up a complicated IF/ELSE/ELSEIF sequence
...
Case 4, 6, 7, 1256
...
Case Else
...
End Select
For 'large' continous ranges:
Dim nDiff : nDiff = DateDiff("d", dtA, dtB) ' computed just once
Select Case True ' <-- dirty? trick
Case nDiff < -15
...
Case nDiff < 0
...
Case nDiff = 0
...
Case nDiff < 11
...
Case Else ' 11 or greater
End Select
now the logic is like snipping of parts of a number line/numerical ray.
PS:
Did you check your assumptions about DateDiff with code like:
>> dtB = Date()
>> dtA = DateAdd("d", -5, dtB)
>> WScript.Echo dtA, dtB, dateDiff("d", dtA, dtB)
>>
15.02.2014 20.02.2014 5