Can I define the toolbar by application

Can I define the toolbar by application?

No, but a single toolbar button (and a command) can be used by many different applications and business objects. Toolbar buttons are reused (or shared) by applications, which is much the same thing.

Take the command "new" for example:

You can make it appear on the toolbar by altering the definition of the command.

You can enable the new command in applications 1, 2 and 3.

When the button is clicked, the command handler in the current application (either    application 1, 2 or 3) will be invoked to handle the command.

This way your users get used to using the single "New" button .... and it means "Make a new one of the thing I am currently working with".