Hi Rita,
I assume 'A', 'B' and 'C' are SimEvents blocks. In which case, you can use the statistics signals from 'A', 'B' and 'C' to achieve what you want by combining the signals with Simulink blocks to implement your logic. You can then use the 'Message Send' block to convert the logical signal to an entity that operates the 'Entity Gate'.
To give you an idea, I have attached an image that shows constant and mod blocks being used to drive the entity gate. You can add more logic along similar lines to achieve what you want.
Krishna
