kmail context menu actions

hello,

Many times I need to translate words from a message,
now, in Firefox I got that option in the context menu provided by a Google (I 
think) add-on.
I know that Kmail is not a web browser and that is very good.
the question is as follows, how do I add an action to the context menu? (if it 
is possible)
for example: 
piping the selected text to a translation program, or a text editor, 
wget the link, 
search Google that text,... 
there are probably more use cases when you wish to pipe the text to an 
external application.

if you know of a way, please share.
if there is no way then I'll post it as wish.

thanks,
YB.