>I need to create a form to show the client messages (that are in a memo field) when invoicing. I want something more interesting than a simple wait mymemo window. To do it in a generic way (to use it for any messages (vendors, parts, etc...), I was thinking about a simple little form that I can call passing the memo field in parameter. But a memo could get big right ? So what append if it is big ? Will it fail ?

By reading your post, I assume that you have a "message" table.
In this case, you just have to pass the message id to the form and let it handle the locate and display part :-)

:-)