Message box to appear while macro is running

I have a user form that runs a macro. The macro performs lots of operations and takes a while to complete. While it is running I wanted to have a message box up on the screen saying something like "please wait". The problem is that if I just use "MsgBox", it will pause the code until ok is clicked. I tried having it load another user form by doing something like:

pleasewaitform.show
(my macro code)
unload pleasewaitform

but the same problem occurs where it won't run the macro until the box is closed.
I know that there is a way to use a timer, but the time that the macro takes will change as I edit it. So I don't really want that. I want the box to pop up when a button is clicked, and stay on the screen while the macro runs, and then close. Is that possible? Thanks.