how to show informative dialog in OnInit

[jsbach]

I've a script that acts as liveupdate for a bigger application. Most code is inside .OnInit function (no section, at least just one section but it's empty).
At a certain point i check if a program is running and i loop until either the user closes it or the loop has run for 30 seconds (after that, it closes the application and main installer is launched).
Well: at present , during loop i show a banner (using msibanner) just to display a message to the user saying application is running: close it within 30 seconds...).

Of course, using msibanner is not nice as i don't need progress bar (just inform the user); in addition the dialog is small in size.
What i need is a standard windows dialog with the message; better it would be it can be dynamically changed.

I can't use page (i'm inside oninit) and i can't move the code in a section (even tried this) because this way i see the installer dialog. In this case i should set always silent but then nothing is shown (i'm using inetload and i do want to show its own dialog).

Even InstallOptions/InstallOptionsEx of course are not appliable.

I'm quite sure it's possible to have a simple dialog - no banner, no progress bar, no input fields. I searched the forum without success. Any hints appreciated.
thanks in advance.