Status message after hitting enter

Greetings Forum...

I've looked for answers on this before posting, but if I missed a related post, my apologies. I've been looking for a solution to display a "Please wait" message to fill an adjacent cell or to show on a user form after hitting the enter key, as the calcuation that takes place takes at least 10 seconds. Everything I've found for a solution is based on when a macro is running, however the calculation is not a macro, it's simply a big calculation that takes place after a value is entered into a specific cell.

Any help or ideas are much appreciated.

Stumped in Cerritos.