In various embodiments, a user grey cell is disclosed. The user grey cell comprises a simplified logical implementation of a black box cell identified in a software and/or hardware design. The internal functionality of the black box cell is undefined, hidden, or encrypted, and thus is not available for timing analysis. The user grey cell for the black box cell provides sufficient clocking and register information to allow for accurate CDC, false path, and multi-cycle path analysis, and provides a way for designers to locate and repair clock domain crossing violations before the design is implemented in hardware. In various embodiments, a method for user grey cell analysis is disclosed. The method comprises identifying one or more black box cells in a user design. The method further comprises determining which of the input and/or output pins of each of the black box cells are in use by the user design. The method further comprises selecting a user grey cell for one or more of the black box cells, wherein a user grey cell comprises a simplified logic implementation for the black box cell, sufficient to perform CDC, false path, and multi-cycle path analysis. The selected user grey cells may be used in place of the black box cells for CDC, false path, and multi-cycle path analysis.