You are still incorrect to say that, yes, but not because of
opened, which is correct because here it is a verb. (
up is not required, by the way.)
It is highly unusual to talk about the opening of a can during dinner.
Aside from that,
soon during dinner is a bit unusual.
And then
has been (a perfect tense) is not used with a
when clause specifying a definite time.
You need:
The can will be opened (up) during dinner.
The can was opened (up) when we had lunch last night.
CJ