SetLocaleInfo, PostMessage

Hi people,

I need some advice on changing the decimal separator in a VBA module for an active Excel application. The code examples I found so far didn´t do the job to the end.
When I change the decimal separator in system settings I can directly see the change occur in the Excel sheets. This I want to do by code.

I used SetLocaleInfo to achieve this, but the result can only be seen in the Excel sheets after closing and opening Excel again. That´s my problem.

So I tried PostMessage and SendMessage but it didn´t help to get the result in a sheet instantly. I´m not sure I used the correct handles and constants.

I need this code for WinNT. Do I use WM_SETTINGCHANGE or WM_WININICHANGE?
Do I have to use HWND_BROADCAST or can I directly address the Excel application that is running the code module with the API functions?
What are the correct HEX values of the required constants for handles and messages for the API functions?
How do I get information on the HEX values for any handle or constant I need for API functions by the way?
A lot of questions for one problem. (You can see this is my first trial with API).
Thanks for any information.

Gunther