calculated field problem

[luigi]

Hello, I have this kind of problem:
if I compose a message in Outlook 2003 as plain text message and the form I
used has some custom field automatic calculated (i.e. a field with function
now() binded with it) when I open the messagge after I sent the read status
change from read to unread even I did not change the message.
It is possible to use different form for compose and for read the item so I
did not get again the message asking me if I wanna save the Item?

I think that this happen because exchange try to convert the plain text in
html on the server (exchange 2003). I did not find any setting to avoid this.

thanks