The temporal evolution during core hydrogen burning of the total mass (top line of each pair) and of the core mass (bottom line of each pair) of a 500   M_⊙ star calculated with the Eggleton stellar evolutionary code (dashed lines) (cf. Yungelson et al. 2008) and with the approximate evolutionary method for very massive star discussed by Belkus et al. (2007) (solid lines). Since the latter gives results which are in sufficiently good agreement with the results of the detailed calculations, but is computationally much faster, it is an excellent candidate for the use in cluster evolutionary N-body codes dealing with a large number of individual stars.