Limiting Text Length, Without a Data Validation

I have a sheet that clients use to import information into our company for use. A bunch of the cells have strict character limits on them via data validations, however, the client pastes the information over from their internal spreadsheets (which deletes the validation/character limit). I've found some macros that disallow paste functions entirely, or delete input automatically if it is pasting over/removing a validation in the cell. The issue is they're entering a lot of information, and need to be able to paste into cells to save time. Does anyone have a work around for this, that would limit the text length while still allowing users to paste in information, maybe with a pop up that states that they've exceeded the character limit? I've tried to use some conditional formatting to highlight cells that exceed the limit, which would be a fine work around too, but they get removed as well when pasted over. Thanks a ton!