Customise message for See Also button

Hi all,

I think I remember seeing a post/article somewhere about customising the message that appears when no topics are associated with the See Also keywords linked to a button. But of course I can't find that reference anywhere.

Does this ring any bells with anyone?

More Details
Create a See Also button linked to keyword "MyList" in Project A.
"MyList" exists in Project B (slave of A), which is not available on the user's system.
Clicking on the button displays the message "Selection is not associated with any topics, please try another selection".

Thanks for any help,
Amber