thank you friend, I see that you mean that don't tell him in advance that I will leave.
I am not sure that I can get the grant, but if I apply for it, it means I am planning to work for him for the 4th year.
The problem I have is that I knew from another PI (who intended to hire me) that my boss got another grant( though I am not interested in this project), and he is planning to keep me to work for him in the next 2 years. But, definitely I don't want!
For this postdoc grant, there is six-month waiting time, and probably I need to quit within this time if I get new job offer. Thta's the reason I donn't want to apply.