H5 Message procedure

I’m new to Clarion please excuse. Regarding:
FEATURE: H5: Global Prompt to override the Message procedure used to create the WEB Messages. Global Web Extension - Advance - Web Message Procedure NOTE: The procedure must comply with the needed prototype.

I’m trying to apply a custom theme to the message page, to do that I am trying to use this feature. I have created a procedure with the same prototype as the default clarion message function. If called manually in H5 the procedure works and displays according to my theme applied to the procedure, but when I apply it to the above-mentioned feature when the app needs to display a message the appbroker breaks.

Any help will be appreciated.