Custom Command id's for WM_COMMAND

I want to know if it is possible to define a custom command to be sent to WM_COMMAND in the window procedure. For instance I made a toolbar and buttons are created with TBBUTTONS each one has a id command variable that can have STD_NEWFILE and things like that assigned to it.

Can I define my own command id like similar to STD_NEWFILE to be sent to WM_COMMAND whenever I select a button.

Strictly saying there are no standard command ids in Windows, and whatever command id you set in control, or menu item, or toolbar button, it appears to be custom.

What is STD_NEWFILE?