Catch IP Address of Local Machine Insted of Server IP Address where the application is deployed at

Hai ,

 I have a survey that will be sent to all the users across a group, This survey application is deployed on webserver and that link will be sent to all the group members.Right now it was capturing the IP  Address of server for all members in group , insted i need each members Local machine IP Address to be sent the database via server.

 I tried using the following two requests but all they are doing is capturing the server ip address:

 String clientName = Request.ServerVariables["LOGON_USER"];

String clientName = Request.ServerVariables["REMOTE_ADD ...