WACC and Valuation

Im sorry if the question comes out to be a dumb one but i cant help but ask. I'm going over past paper questions and i notice when calculating the WACC to calculate the Market Value of equity we multiply the EX-DIVIDEND share price with amount of shares and then discount it as a step to figure out WACC. But in business valuation when using DVM as a model to value the business the share price which is used is CUM DIVIDEND because dvm basically gives you the cum-dividend price per share. I dont quite understand why is ex-dividend used for finding out market value but when valuation using dvm they use cum dividend to find the market value?