How i can change the no permission message ?

That's not customizeable in PEX 1.x and I don't know if it's customizable in PEX 2.x which is still in development. (I suspect it is not.)

It's not -- the no permission message is chosen by each plugin. PEX just gives the plugin a yes or no when asked, and the plugin uses that to determine what to do and what messages to send.

Ahhh! That's right. Now I remember you saying that before. Sorry for making you repeat yourself. :X