Nice to see Cowboys fans whining on another forum, but don't blame the refs for knowing the rules a helluva lot better than your sad sack coach.
OFFENSIVE SUBSTITUTIONS Article 5 The following are applicable to any offensive substitute who is entering the game: (a) He must move onto the field of play or the end zone as far as the inside of the field numerals prior to the snap to be a legal substitution. If he does not, and is on the field of play or end zone at the time of a legal snap, he is an illegal substitute. (b) If he approaches the huddle and communicates with a teammate, he is required to participate in at least one play before being withdrawn. Violations of this rule may be penalized for unsportsmanlike conduct.