Author: Jonas Bilinkevicius

Is there a way to change the decimal point (.) on the numeric keypad to a comma (,) 
on the application level?

Answer:

You can use a handler for the Application.OnMessage event. Changing the decimal 
separator produced by numpad globally:
1   
2   procedure TForm1.AppOnMessage(var Msg: TMsg; var Handled: Boolean);
3   begin
4     case Msg.message of
5       WM_KEYDOWN, WM_KEYUP:
6         if (Msg.wparam = VK_DECIMAL) and (Odd(GetKeyState(VK_NUMLOCK))) then
7         begin
8           Msg.wparam := 190; { for point, use 188 for comma }
9           Msg.lparam := MakeLParam(LoWord(msg.lparam), (HiWord(Msg.lparam)
10            and $FE00) + MapVirtualKey(Msg.wparam, 0));
11        end;
12    end;
13  end;