This paper presents a programmable frequency scan algorithm based on harmonic balance. The core idea involves treating systems under perturbation as nonlinear time-periodic (NTP) systems. Steady-state harmonics are first solved via Newton‒Raphson iteration through a set of nonlinear equations, and then input-output variables are selected to estimate the linear transfer function of the original NTP system without perturbations. The applications and insights of the proposed algorithm are discussed, particularly in guiding existing frequency scan algorithms, which are restricted by time-domain signal generation or measurement. This improvement is achieved through linear stability analysis of NTP systems with perturbations.