I assume you are talking about a web application. You can use the CGI Field "Remote_Addr" to get the IP address of any incoming browser client. You retrieve this through the Query_String and Query_String_Decoded fields in your web enabled form. Look into Domino help to find out the best way to implement the Query_String_Decoded fields on your form. From there, you can pull out the "Remote_Addr" portion and you will have your IP Address.
This was first published in August 2001