How to write a infinite sum FOC into dynare

Dear All:
I am new to dynare.I want to know how to to write a infinite sum FOC into dynare ?(something like FOC of calvo price setting)
thanks !

Generally, you must either use a linear approximation that gets rid of the infinite sum or you find a recursive formulation of the infinite sum that makes it representable as a finite object (as Schmitt-Grohe/Uribe did for the Calvo pricing example).