It is my understanding from talking with many priest, a few canon lawyers, a few Bishops, and one Cardinal, that you, if not a priest, may receive the Holy Eucharist only once in a calendar day, EXCEPT if the SECOND time is for a different purpose, such as a wedding, funeral, baptism, etc. Under that understanding, if you are receiving the Holy Eucharist at the Saturday Evening Vigil, which is technically the Sunday Mass, you may not then receive the Holy Eucharist at Sunday Morning Mass, unless that Mass for for a different purpose.
Some have used the “loop hole” of Mass is being said Saturday evening on behalf of X intentions, and on Sunday morning for Y intentions, but the Canon lawyers I have talked to feel that was “against the grain”.
In Christ,
Friar Don, OBR