With the function below you can determine if a cell is within a given range:

Function InRange(Range1 As Range, Range2 As Range) As Boolean
' returns True if Range1 is within Range2
Dim InterSectRange As Range
    Set InterSectRange = Application.Intersect(Range1, Range2)
    InRange = Not InterSectRange Is Nothing
    Set InterSectRange = Nothing
End Function


Sub TestInRange()
    If InRange(ActiveCell, Range("A1:D100")) Then
        ' code to handle that the active cell is within the right range
        MsgBox "Active Cell In Range!"
    Else
        ' code to handle that the active cell is not within the right range
        MsgBox "Active Cell NOT In Range!"
    End If
End Sub