Q: My pastor isn’t available for two of the masses this weekend, and he asked me to lead a communion service at those times. Is that all right?
A: No. If you have any mass at all at the church this weekend, then you may not have any communion service on the same day in the same place – even if it’s a Saturday night mass, even if it’s in another language. Even without that prohibition, you would need the bishop’s permission under normal circumstances.
See the Vatican Office of the Congregation for Divine Worship’s 1988 “Directory for Sunday Celebrations in the Absence of a Priest,” paragraphs 21 and 24.