SQL & PL/SQL

hi want a small help ...
I have a
procedure p1(p1 in number default 2, p2 in number default 3)
begin
:
:
:
end;

When the procedure will be called without passing parameters it will execute with default parameters.
That time I want to dispay message saying
" AS paramters are not passed, procedure is being executed with foll. default parameters:
Param 1 = 2
Param 2 = 3 "

Now issue is how do I capture this condition that , the parameters are being passed and it is using default parameters ?

Thanks