We investigate a general class of dynamical open-bid combinatorial auction protocols termed price-demand procedures, where the auctioneer asks buyer-dependent price vectors and buyers reveal demand sets. Such revelations are easier to practice than the revelations of entire valuations at once. With revealed preference activity rule and connectedness, we characterize the class of all procedures that achieve the VCG outcome correctly. Since buyers can detect whether the auctioneer succeeds to achieve the VCG outcome just by observing the history, they can leave the selection of procedure the auctioneer’s discretion. The auctioneer can save irrelevant information leakage by selecting a signal-contingent shortcut.