Due to the inherent complexity of the general Lifshitz theory, the Hamaker-De Boer approach is still used in computing the van der Waals attractive force in systems with macrobodies of complex shapes. To account for the retardation of force computed by this approach, the London equation has in the past been modified by introducing correction functions. However, the functions proposed in the past are either piece-wise in nature or valid for a restricted range of separation distances, making it difficult to carry out the necessary integrations in cases involving complex macrobodies. In this paper, a single correction function is proposed. First, the correction function is shown to represent the retardation effect reasonably wed by comparing the proposed function with those proposed in the past. Then, the retarded van der Waals energy is computed for nine different systems involving mica, quartz, pyrophyllite, water, polystyrene, and air for the case of two semi-infinite parallel plates separated by a medium. Experimental data found in the literature on the dielectric frequency spectra are utilized. The results are compared with those computed by the general Lifshitz theory and are shown to agree reasonably well.