VBS get number of occurrences

Find = chr(34)
Str = "This is string with " & chr(34) & "double quotes" & chr(34) & "."
Occurrences = (Len(Str) - Len(Replace(Str,Find,Empty)) / Len(Find))
MsgBox	"String: " & Str & vbCrLf &_
	"Contains :" & Occurrences & " occurrences of: " & Find & "."
	
Function GetOccurrences(InputString,LookupString)
	If	_
		IsNull(InputString) Or IsEmpty(InputString) Or _ 
		IsNull(LookupString) Or IsEmpty(LookupString) _
	Then
		GetOccurrences = 0
	Else
		If Len(InputString) = 0 Or Len(LookupString) = 0 Then
			GetOccurrences = 0
		Else
			GetOccurrences = (Len(InputString) - Len(Replace(InputString,LookupString,Empty)) / Len(LookupString))
		End If
	End If
End Function