Excel cell width

We have a spreadsheet that our customers can enter their employees data into. I used the Data Validation feature to make cells only hold a certain number for positions (like 25 characters for the address line 1 field) but if the customer uses their database, and its field is say 30 characters, and they cut & paste then the field I set up ends up with 30 characters, even though I put a limit of 25 on it. Is there a way to lock the field where they can’t do that?