In this work, we demonstrate and quantify the variation of interference with time, and its effect on capacity of a cellular CDMA system. We compute the value of interference for various cases using simulation and analytical methods. The values of interference obtained agree with the results obtained in previous literature. We investigate the effect of change of propagation path loss constant, number of mobile users and velocity of users on the interference. Our results show that the average normalized outside cell interference is independent of the number of users (as expected), and under certain conditions is also independent of the velocity of the users. The maximum value of interference is much higher than the mean value, showing us interference varies substantially with time.