This means that the Range B1:B10 is blank / empty / does not have data :
Code:
If Application.Intersect(Target, Range("B1:B10")) Is Nothing Then
This means that the Range C40 has data / is not empty / is not blank :
Code:
If Not Application.Intersect(Target, Range("C40")) Is Nothing Then
When you see two negatives "Not" / "is Nothing" .. think in terms of your High School Algebra : Two Negatives make a positive.