Work is really busy, so I want to skip the meeting that's in three days.
I have my hands full with work, so I want to be absent from the meeting in three days.
「業務が立て込んでいるので、明々後日の会合は欠席したい。」は英語で「Work is really busy, so I want to skip the meeting that's in three days.」という表現が良いと思います。
「業務が立ち込む」は英語で「To be busy」や「To have one's hands full with work」という意味があります。「会合」には「Meeting」や「Gathering」という意味です。「明々後日」は「In three days」、「Two days after tomorrow」です。