sub for a sub

[todd66]

Is it legal for a substitute to be substituted for during the same dead ball period? example: A2 is waiting at the table to sub for A1. At the next dead ball opportunity, A2 enters the game for A1. B2 also subs in for B1. Coach A sees this and does not like the matchup between A2 and B2 and sends A3 to the table for A2. Is this legal? Please cite rules to support your answer.