Updating the controltip text is trivial.

me.txtControl.ControlTipText = "Something you want to see"

This will change it for display purposes only.  Hence, the design of
the form will retain whatever was in ControlTipText; so in the future
if it isn't "set" for some reason it will go back to what it was.

Now, as far as putting a timestamp in there.  What a horrible design
idea (strong letter to follow).  If you want to display the date/time
that the record was last updated, feel free to do so, and if you have
absolutely no real estate left on your form, use the status bar.

Why make the user move his/her mouse and wait for the ControlTip to
pop up when that isn't being used to further the user's input decision
on the control in question.  Bad.  Very bad.

One more thing.  Access doesn't automatically store a datestamp as to
when a record was last updated and by whom.  If you want that you will
need to store it yourself.  The good news is that since you will be
the one doing the storing, you will then know where it is so you can
retrieve it when you place it on the form or in the status bar.

mike