vba filter question

[bensonsearch]

I have the below code

If ComboBox3.value <> "" Then
       Worksheets("Sheet3").Range("A1:P" & lastrow).AutoFilter _
        Field:=9, Criteria1:=">=" & tempc
End If

tempc is the value of the box ie 3, tempc is also a integer

the filter works fine but if there is no 3 in the field it returns ALL records. any ideas why?