Hello,
I have two general questions:

Does Dynare solve models with inequalities?
I need bound a variable in my model in interval [0,1]. Few others vars I have to make positive.
I tryed:
model;
mu>=0;
mu<=1;
…
But it doesn’t work.
How can I bound variables in Dynare? 
May I determine exogenous variables within Dynare code?
I’m trying to put an equation for exogenous variable ‘a’ :
model;
a = 0.9*a(1);
…
but it results error: “exogenous variable has lag…”.
Thanks,
Oleg