Just add an if statement. For instance if you want to only download excel files then the below should work.

[vba]Public Sub saveAttachtoDisk(itm As Outlook.MailItem)
Dim objAtt As Outlook.Attachment
Dim saveFolder As String
saveFolder = "c:\temp"
For Each objAtt In itm.Attachments
stFileName = saveFolder & "\" & objAtt.DisplayName
i = 0
JumpHere:
If Dir(stFileName) = "" Then
if ucase(objAtt.DisplayName) like "*.XLS" then
objAtt.SaveAsFile stFileName
end if
Else
i = i + 1
stFileName = saveFolder & "\" & i & " - " & objAtt.DisplayName
Goto JumpHere
End If
Set objAtt = Nothing
Next

itm.Delete

End Sub [/vba]

As for attachment size I got this from google. Don't have time to implement it into this code but it should get you started.

http://www.add-in-express.com/creati...tachment-size/