Avoid duplication in copying

[roshappu]

Hi I am copying data from a worksheet in txt format (File name : Nov 2007) using macros to another excel file . The data is consisting of 200 records staring with month name "Nov 2007" . I want the macro to check and warn me if someone again opens the file Nov 2007 txt file so that the november records are again not duplicated in the excel file . what is the code which i can use to avoid this duplication

[SamT]

Something like

if not Range("A:A").Find("Nov 2007") is nothing then Exit sub