Becki,
You need to constantly reevaluate.
When my Wink vomited, I set the alarm for every two hours, checked for vomit, tested him. No food unless he was lower than 200. Then only a little, 1 Tablespoon MAX. Different insulin though.
No, no shot tonight.
Get a test before feeding in the am.
Feed him, make sure he keeps it down.
Don't let him eat three cans.
As soon as he finishes eating 1 can, test again.
If his bg is higher than 200, then give him his 1.5 unit shot.
and he can have more food, 1/2 to 1 can more.
Test him again as soon as you get home.