There may be an instance in which voiceover from another point in time can be employed over a visual scene or montage. Often, using (V.O.) beside the speaking character name will communicate what is needed, but if it is confusing, you may add what clarifying words you need in the parentheses.
EXT. BOARDWALK – NIGHT
Under the moonlight, ice cream melts into a pink puddle.
ALLISON (V.O. FROM AFTERNOON)
I love ice cream!
A lonely dog sniffs the melted ice cream. Runs off with the cone.
JOE (V.O. – SAME)
What flavor did you get?
A fresh sneaker steps in the gooey mess.
The sneakered man shakes his fist at the heavens.
Essentially, do you what you have to do so that it makes sense to the reader. Formatting conventions are there to help with clarity, but if they are getting in its way you can take some liberties.