This article deals with the problem of temporal and parametric formal validation for discrete event systems. It particularly focuses on the time Petri nets formalism, for which the parametric property verification with model checking is still a non resolved problem. A method is proposed, combining no parametric timed model checking with classical iterative algorithms to avoid combinatory explosion of the analysis process. Algorithms are proposed for the verification of several property types into two specific hypothesis, depending on the parameters values. They have been implemented into a tool: LPT (Little Parametric Tool), which has been used to validate a buffer management system to illustrate the given method.