I have developed an excel/VBA workbook for processing and displaying
sensitive commercial information. I'd like to use the workbook for a number
of clients, but need to ensure that when I pass a "clean" copy to a client,
he/she will not be able to recover information "left over" from a previous
client's processing.

My question is: If I delete information from a worksheet, save under a new
name and then email the new version to someone, how do I ensure that the
deleted information cannot be recovered at a later date, either using built
in tools or specialist data recovery techniques/software?

Many thanks for your help.