Open a popup form showing the message. Being a popup it will stay on top.
Turn off Echo if you don't want the background stuff to be seen happening.
Close the popup form and enable echo when the task completes.
You could also consider running the background stuff hidden to stop it appearing at all.
if you want something simple but visually pleasing, why don't you have the form only open during the recordset stuff and close when finished then put an animated gif or something to that effect so it is perpetual movement and non specific but showing that something is happening.
Google has something similar with 4 coloured balls moving left to right etc.