A computational procedure based on the arclength continuation method is designed for finding a se-quence of solutions on variations of specifications in stagewise separation processes. The arclength continuation method can be implemented simply with an existing code that solves the modelling equations by Newton-Raphson method. The procedure is capable of direct handling of functional form specifications as varying varying variables. In order to promote the computational efficiency, emphasises are given to generation and handling of Jacobian matrices and cal-culation of integration step-sizes. The applicability of the designed procedure to the problems with multiple solutions is shown on numerical examples.