This requirement is a kind of very very special … I could imagine that it’s gonna hard to find an already existing script for this particular task. You will have to piece something together yourself I’m afraid.
I’d recommend to take a look at the great module ImportExcel by Doug Finke. It should make it easy to read and write existing Excel files.
Adding to what @olaf-soyk mentioned, use Import-Excel,Export-Excel cmdlet from ImportExcel module with a ForEach-Object in between to trim what you don’t want.
Import-Excel <file path > | ForEach-Object -Process {
# use $_.WhatEverColumn and use split or trim
} | Export-Excel <dest file path>