>I have project of a software where many ujavascript:document.Form1.submit()sers will feed a table and then
>I will join all tables (equipaments_failures_and_solutions.dbf)
>
>The table may become very large
>
>But I would not like this .dbf be stolen and displayed in other software other than mine
>
>I would like to encripty it with chrtran() funcion

I don't think this will be a very safe encryption. However, it may be sufficient for your needs.

>But I have some doubts
>
>1-Can I use function in form texbox values ?

Well, I don't think you can use the .ControlSource property. You will have to use additional commands to load the value, and save it back to the database.

>2-How will this affect the application speed ?

If you encrypt/decrypt one record at a time, it should go quite fast. Searching for a certain value on an index should also be feasible - just index on the encrypted field, and search on an encrypted value.

If you need to decrypt hundreds or thousands of records for some processing, it will become slower, of course.