Access value of a lookup field

Access value of a lookup field

A simplified version of a problem I have:

I have two forms Projects and Clients.

Projects has a lookup field Client which looks up field Client on form Clients.

I want to access the value of Client.

In a Field Action on Client on User Input I have the Deluge command  'alert "Entered: "+input.Client' . 

The message box shows "Entered: 2440810000000112935".

How do I get the value of Client.

Thanks!