How do I make an integer to null in Excel VBA?

I am trying to detect whether an i开发者_如何学Pythonnteger was set, and if not, skip most of the code in the loop (using an if statement). Here is what I have so for.

Do While hws.Cells(r, 9).Value <> ""
    On Error Resume Next
    ar = Null
    ar = aws.Range("A:A").Find(hws.Cells(r, 2).Value).Row
    If Not IsNull(ar) Then
  'work with ar'
    End If
    r = r + 1
Loop

However, when I run it, ar = Null has problems. It says "Invalid use of null".

Variables defined as Integer cannot be Null in VBA. You will have to find another way to do what you want. eg use a different data type or use a magic number to indicate null (eg -1).

In your example code, either ar will be assigned a Long value (Range.Row is a Long) or it will throw an error.

just use a variant and isempty:

Dim i

If IsEmpty(i) Then MsgBox "IsEmpty"
i = 10

If IsEmpty(i) Then
   MsgBox "IsEmpty"
Else
   MsgBox "not Empty"
End If
i = Empty
If IsEmpty(i) Then MsgBox "IsEmpty"
'a kind of Nullable behaviour you only can get with a variant
'do you have integer?
Dim j as Integer
j = 0
If j = 0 Then MsgBox "j is 0"

Find returns a range:

Dim rf As Range
With aws.Range("A:A")
    Set rf = .Find(hws.Cells(r, 2).Value)
    If Not rf Is Nothing Then
        Debug.Print "Found : " & rf.Address
    End If
End With

-- http://msdn.microsoft.com/en-us/library/aa195730(office.11).aspx